During 1992, 672 rainbow trout Oncorhynchus mykiss were sampled using hook and line gear from two study reaches in Lake Creek and the Talachulitna River and from one study reach in Peters Creek. In addition, 142 rainbow trout were sampled from the Deshka River using both electrofishing gear and hoop traps. Rainbow trout ranged in fork length from 190 millimeters to 552 millimeters and age ranged from 2 to 8 years. At all sites, the mean length-at-age increased with age. Significant differences occurred in mean lengths, length distributions, age compositions, and mean length-at-ages of rainbow trout captured between some reaches in study streams and between some study streams between years. In combination, these data suggest that multiple stocks of rainbow trout inhabit the Susitna River basin. Limited recovery of tagged fish, however, suggests that migrational movements occurred between some study reaches, and between some streams. Fish captured in upper Lake Creek were recaptured in lower Lake Creek, and fish captured in the lower Talachulitna River were recaptured in Shell Creek. Significant differences in age composition and mean length-at-age for select Susitna River tributaries sampled during 1989, 1990, 1991, and 1992 suggest that age and size compositions vary annually. Such findings make management for historic size and age compositions difficult, and show the importance of collecting data over a period of years. Lastly, the occurrence of few trout over 510 millimeters fork length (the size limit defined in the Cook Inlet Rainbow Trout Management Plan for trophy trout) and the slow growth rate of Susitna River basin trout relative to other Alaskan waters containing trophy trout suggest that Susitna River rainbow trout stocks are not viable candidates for management as trophy fisheries under the Cook Inlet Rainbow Trout Management Plan.