Regular season
| Year | Team | Games | Att | Cmp | Cmp% | Pass Yds | Pass TD | INT | Sacks | Y/A | Rating |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1979 | SF | 16 | 23 | 13 | 56.5 | 96 | 1 | 0 | 0 | 4.2 | 81.1 |
| 1980 | SF | 15 | 273 | 176 | 64.5 | 1795 | 15 | 9 | 15 | 6.6 | 87.8 |
| 1981 | SF | 16 | 488 | 311 | 63.7 | 3565 | 19 | 12 | 26 | 7.3 | 88.4 |
| 1982 | SF | 9 | 346 | 213 | 61.6 | 2613 | 17 | 11 | 20 | 7.6 | 88.0 |
| 1983 | SF | 16 | 515 | 332 | 64.5 | 3910 | 26 | 12 | 33 | 7.6 | 94.6 |
| 1984 | SF | 16 | 432 | 279 | 64.6 | 3630 | 28 | 10 | 22 | 8.4 | 102.9 |
| 1985 | SF | 15 | 494 | 303 | 61.3 | 3653 | 27 | 13 | 35 | 7.4 | 91.3 |
| 1986 | SF | 8 | 307 | 191 | 62.2 | 2236 | 8 | 9 | 12 | 7.3 | 80.7 |
| 1987 | SF | 13 | 398 | 266 | 66.8 | 3054 | 31 | 13 | 22 | 7.7 | 102.1 |
| 1988 | SF | 14 | 397 | 238 | 59.9 | 2981 | 18 | 10 | 34 | 7.5 | 87.9 |
| 1989 | SF | 13 | 386 | 271 | 70.2 | 3521 | 26 | 8 | 33 | 9.1 | 112.4 |
| 1990 | SF | 15 | 520 | 321 | 61.7 | 3944 | 26 | 16 | 29 | 7.6 | 89.0 |
| 1992 | SF | 1 | 21 | 15 | 71.4 | 126 | 2 | 0 | 1 | 6.0 | 118.4 |
| 1993 | KC | 11 | 298 | 181 | 60.7 | 2144 | 13 | 7 | 12 | 7.2 | 87.4 |
| 1994 | KC | 14 | 493 | 299 | 60.6 | 3283 | 16 | 9 | 19 | 6.7 | 83.6 |