24
There are 696 episodes of classic Doctor Who (not including the TV movie), comprising 157 different stories. However a large number of these episodes (108 in total) are 'lost' and it is thought copies no longer exist. The First Doctor: 29 stories (134 episodes) The Second Doctor: 21 stories (119 episodes) The Third Doctor: 24 stories (128 episodes) The Fourth Doctor: 42 stories (172 episodes) The Fifth Doctor: 20 stories (69 episodes) The Sixth Doctor: 8 stories (31 episodes) The Seventh Doctor: 13 stories (43 episodes)
The Seventh Doctor appeared in 43 episodes (comprised of 13 stories).
The Fifth Doctor appeared in 69 episodes.
21
42
31
415 separate stories.
Up to Journey's End 198 stories 751 Episodes
There have been 753 episodes in Doctor Who.
Expanding your question to 2008 (as it is now as I'm answering, so up until the last episode of Season 4 of the new series, Journey's End)... There have been 202 stories (if you include the unfinished Shada) comprising 757 episodes. And if you don't count Shada, 201 stories 751 episodes.
There are 13 episodes in every season of Doctor Who.
there has been about 777 episodes of Doctor Who