A trial was conducted to evaluate the effects of the number of feeding days on feed consumption and growth of rainbow trout. Oncorhynchus mykiss (Walbaum) (initial mean weight 53.6+/-1.3 g). Fish were held under natural winter-spring (40 degrees 57'N) photoperiod (L:8 D:16 - L:14 D: 10) and ambient water temperatures (4-12 degreesC) for 128 days, and fed on day 7 (F-7), day 5 (F-5.1: no feeding on weekends and F-5.2: no feeding on Sundays and Wednesdays) or every other day (F-EOD). Feeding treatments were replicated with 50 fish held in 200-L tanks. Number of feeding days affected final lire weight, with fish in group F-7 achieving a mean weight of 285.6 g, followed by F-5.1 (256.6 g), F-5.2 (247.6 g) and F-EOD (223.2 g). Final condition factors (CF) differed between the F-EOD group and the others. Feed conversion ratios (FCR) exhibited significant differences among some of the groups. The results suggest that depriving rainbow trout of feed for more than 1 day a week has a negative effect on growth, hut little influence on feed conversion.