Four experiments with marked, legal-sized, hatchery-reared, brown and rainbow trout were conducted on portions of five Michigan trout streams to determine which season of release would yield the greatest return to the angler. Equal numbers of tagged or fin-clipped fish were planted in the fall after the close of the trout season and in the spring before the trout season opened. In two experiments, larger numbers of fish were also released during the fishing season; May, June, and July. In three of the experiments, angler returns were obtained by voluntary reports and by partial creel census conducted during the first season that marked fish were present. In the fourth experiment, all recoveries were reported voluntarily. Almost 63,000 fish were planted, and recaptures of 1,173 brown trout and 2,307 rainbow trout were reported. In six tests with rainbow trout and four tests with brown trout, spring planting yielded significantly higher returns than did fall planting. In two tests with brown trout, spring planting yielded higher returns, but its superiority over fall planting was not statistically significant.