Where Dragonball ends and Dragonball Z really begins

[The Prince]

The beginning of Dragonball Z is perfect in itself because it's a major change for the show. Gohan fills Goku's place as the young promising fighter.

Though the "feel(story,story)" of Dragonball really ended for me when Goku beat Tien in the tournament. All of Goku's previous challenges had been beaten and he had become "unreal" in his abilities. No human could match him, humans were becoming obsolete and it showed. Tien the second(in not first) most dedicated fighter was beaten, Roshi didn't even enter, Kuririn was beaten be an "alien", and Yamcha would soon be crushed my Kami(another non-human) completing the ascension of Goku as being in a class of his own. Tien could compete but his defeat was the climax of the show for me. After that the style of the fights changed dramatically, power levels became the major and almost complete deciding factor in a fight. Tien and others had incredible techniques but he was only human and couldn't compete against a saiyan.

Goku and Piccolo's fight was such a different style from Dragonball, all the previous fights were completely different, and I didn't feel like I was watching the same show anymore. Everyone watching with all their hopes resting in Goku's hands, sadly the tone of most of Dragonball Z...

[Rocketman]

Well, maybe after the Cell saga on...

Ha. The Cell Saga is the worst offender.

[PiccoloDaimao]

Yeah, for me personally that "DBZ feel" comes during the 23rd Budokai. The battles start to incorporate flying and ki blast on a regular basis.

[FunkmastaZeph]

DBZ starts when Piccolo Daimou kicks Pilaf off his ship.
Anyone thinking the story past that point is still carefree and goofy may need to reread.

[Kaboom]

Come to think of it, the first instance of the word "Saiya-jin" could kinda mark the point the series turned.

[Jodaku]

I'm generally with Roketman on this; stroy-wise I would consider Dragonball to be from the beginning to the all the way through to the end of the Freeza saga and everything after I would class as 'Z', although I'm not as harsh with the 'Z' stuff as Rocketman is, it is overall markably inferior to what came before it, and kinda ruins what would've been a really great strory had it stopped at Freeza.

In regards to the 'feel' of the series, the turning point was definitely post- 22nd Budokai, and I would argue that in terms of sheer rawness and intensity it peaked at the Goku Vs Piccolo fight at the 23rd, and although it came really close during parts of the Saiyan and Freeza sagas, it never quite got to that level again (although Goku Vs Freeza is compensated with the sheer epicness and scale of the battle against sheer 'oomph' that Goku Vs Piccolo had).