Field and laboratory observations revealed tidal and diurnal cues for spawning in the Atlantic silverside, Menidia menidia. In the field, spawning runs began near the time of daytime high tides at flood tide velocities ranging from 3 to 16, X 11 cm sec. Spawning runs ended at ebb tide velocities ranging from 5 to 22, X 17 cm sec. In the laboratory M. menidia were reared from embryos to sexual maturity in 10 months (April 1979 to January 1980). During this time, approximately 50 fish were held in each of two, 1 m diameter tanks. A pump was used to maintain a constant current velocity of 8 cm sec 1 in the holding tanks. Water temperature ranged from 16 to 25C, the salinity was 30 + or - 2 0/00. Fish were fed Tetra-min flake food and Artemia nauplii each day. During January 1980, the seawater circulation pump was turned off twice daily for one hour, 1200 to 1300 and 2400 to 0100. Current velocities decreaded from 8 cm sec 1 to 0.0 cm sec during these periods. (Copyright (c) 1983, Dr. W. Junk Publishers.)