Growth, yolk sac absorption, and maximum wet weight of alevin rainbow trout (Oncorhynchus mykiss) stocked in fresh water (0 salinity), water with 4 parts per thousand salinity, or water with 8 parts per thousand salinity were determined. Larvae were sampled on the 329th degree-day when 50% of the eggs hatched, and on degree-days 361, 396, 432, 467, 496, 528, 557, and 584. Sampled larvae were anesthetized in benzocaine solution (20 mg/l) and preserved in 10% formaldehyde. At hatching, mean length was 14.25 +/- 0.63 mm and total wet weight was 58.16 +/- 9.98 mg. Larvae reached the swim-up stage at 96.94 +/- 8.71 mg on the 28th day in fresh water, at 120.29 +/- 9.26 mg on 19th day in 4 parts per thousand salinity, and at 102.80 +/- 5.88 mg on 22nd day in 8 parts per thousand salinity. The total length and dry weight of the larvae at the swim-up stage differed significantly among treatments (p<0.001). There was a significant relationship between larvae dry weight and degree-day. The best growth, yolk sac consumption, and alevin wet weight were obtained in 4 parts per thousand salinity.