Larvae (eleutheroembryos) of cisco Coregonus albula and whitefish C. larvaretus started to drift downstream in the Gudbrandsdalslågen River concurrently with the beginning of the spring freshets each year, 1981–1983. The duration of yearly outdrift lasted 2–5 weeks in late April and May. The yearly maximum out-drift was positively correlated with the rate of increase in water discharge, but not with water temperature during spring. Most larvae drifted downstream during night.