Everything is fine until a strange warrior named Raditz lands on Earth he finds Goku who is in the middle of a reunion with Master Roshi, Krillin, Gohan and Bulma and informs him that he is Goku's brother and, like Goku a warrior from another planet called a Saiyan. Raditz tells Goku that he was sent to Earth to exterminated all life and prepare it for sale but Goku had forgotten his mission when he fell into a ravene and bumped his head. Raditz offered Goku to join him in the planet conquering business but he was turned down. Angred by this Raditz kidnaps Gohan.
Extremely overpowered, Goku teams up with his enemy Piccolo. Although they are both attacking at the same time they are still no match for the evil Saiyan. Then Piccolo has an idea, to use a new attack however it takes a while to charge it up so Goku would have to face Raditz alone for five minutes. Goku puts up a good fight but gets quite beaten up. While Raditz is distracted Piccolo fires the Special Beam Cannon (Makankosappo) but he misses. Meanwhile angry at the pain Goku had been receiving Gohan breaks free of the space pod he was in and head buts Raditz greatly weakining him.
Goku at this point grabs Raditz and gets him in a hold.Goku tells Piccolo to again fire his attack which he does and it goes straight through both of them they die in a matter of minutes.
Before he dies, Piccolo tell Raditz of the dragonballs. Raditz then informs him that his scouter is also a transmitter and that two more Saiyans will come to Earth in one year.
Meanwhile in heaven Goku is granted permission to go to King Kai's for special training the only problem is where he lives is on a small planetoid at the end of a 10,000 mile snake path. Months pass on snakeway but Goku is still not at King Kai's and is very tired. He is offered a ride by a passing demon but he falls off and into the land of no return. Goku is informed that the only way to get out is to face the two demons of hell at a contest which Goku easily wins. Goku is shown the way out but to his dissapointment the "exit" brings him straight back to the beginning of snakeway and he has to start his journey all over again.
Meanwhile, Piccolo and Gohan are doing some training in the wilderness. Including Piccolo abandoning Gohan in the wilderness for 6 months by himself where he has to face meat eating dinosaurs. Surprisingly Gohan does quite well on his own. After the six months are up Piccolo begins a brutal training routine and finally Gohans power begins to surface.
Krillin, Yamcha, Tien, Chaozu and Yajirobe are also training at Kame's palace and use various methods including a battle with the Saiyans of the past and each raises their power levels by a thousand.
When Goku finally reaches King Kai's he undertakes a series of training methods including chasing his pet monkey Bubbles and hitting a grasshopper over the head (all in 10 times the Earth's natural gravity) but he accomplishes them anyway. Finally King Kai manages to teach Goku some techniques including the Spirit Bomb and the Kaioken power up. With the Saiyans arriving in a few days Goku has to maken the trip back along snakeway but King Kai had forgot to account this into the plan, luckily Goku's training had greatly improved his power and speed.
A year after Raditz warned about the Saiyans proves to be true as two Saiyans land in a heavily populated city and destroy it (and the people). After destroying it they head to battle the fully trained Z warriors. The check their power levels and notice that Piccolo is an alien called a Namek (which surprises him and Kami).
The Saiyans decide to grow some beings known as Saibamen each is as powerful as Raditz was and they will fight the Z warriors.
Krillin tells Vegeta that they would have more of a chance if they waited for Goku and Vegeta decides to wait three hours for Goku to show up. They wait for three hours but Goku still is not there. The battle resumes when Vegeta notices that Goku is coming and has a higher power level than he expected and tells Nappa to quickly finish the others off before they can help Goku and evil as he is, Nappa decides to kill Gohan first but Piccolo puts himself of Nappa's blast and is killed. By the time Goku arrives at the battlefield only Gohan and Krillin are left. Goku is angered by the death of his friends but maintains his cool and fightts Nappa, however this time Nappa is unable to land any hits and Vegeta finishes him off.
Goku then takes on Vegeta and using the Kaioken power up his able to badly injure Vegeta but it puts great strain on his body. Seeing that he is overpowered Vegeta transforms himself into an Oozouru with the help of an artificial moon. Goku is chased around by the massive ape and uses a Solar Flare to blind Vegeta so he can form a spirit bomb. However, Vegeta recovers before he can use it and most of the energy is lost. Vegeta grabs on to Goku and crushes him but Yajirobe sneaks up behind him aand cuts off his tail which turns Vegeta back to normal.
With Goku too injured to fight, Vegeta does battle with Gohan. Meanwhile Goku tells Krillin to take the remainder of his spirit bomb. Gohan is about to be defeated, Krilin fires the ball at Vegeta. He dodges it but Gohan bounces it back and hits Vegeta from the rear.
Thinking Vegeta is dead, Everyone begins to celebrate - except Goku who tells them that he is still very much alive and will be back soon. Gohan and Vegeta resume their battle and it looks like Vegeta will win until Yajirobe slices Vegeta in the back with his sword and when he recovers he kicks the crap out of Yajirobe. This gives Gohan time to stare up at the moon and transform into Oozouru.
With little energy left, Vegeta is smacked around by Gohan with no options left Vegeta opts to use a Destructo Disk to cut off Gohan's tail. But he doesn't have enough strength to move out of the way of the monkey's massive body and is painfully crushed by the ape. Vegeta calls for his space pod and begins to crawl toward it but Krillin refuses to let him go and puts Yajirobe's sword up to Vegeta's throat but Goku begs him to spare Vegeta's life and Krillin reluctantly agrees but Vegeta vows to return and flies away...