See Some of the Longest Running Television Comedies for updated info, and also see simpsonsmath.com

Longest Running Sitcoms (2001)

By number of seasons:
14 (The Adventures Of) Ozzie And Harriet
13 The Simpsons
12 My Three Sons
11 M*A*S*H, Cheers, The Danny Thomas Show / Make Room For Daddy, Happy Days, The Jeffersons, Married ... With Children
10 Murphy Brown
9 Alice, Roseanne, Family Matters, Coach, Frasier, All In The Family

By number of episodes:
435 Ozzie & harriet
392 My Three Sons
336 The Danny Thomas Show / Make Room For Daddy
278+ The Simpsons [291 by spring 2002]
275 Cheers
262 Married with children
256 Mash
255 Happy days
253 The jeffersons
252 Bewitched
249 The andy griffith show
247 Murphy brown
234 Leave it to beaver
222 Roseanne
214 Family matters
210 All in the family
209 Facts of life
207+ Frasier
204 Home improvement
202 Alice
201 The Cosby Show
200 Coach