Between May and July 2002, we conducted a field study to investigate possible environmental factors influencing surf smelt (Hypomesus pretiosus) egg mortality at eight beaches on the southern Strait of Georgia, British Columbia (B.C.), Canada. Egg mortality was variable, but was positively correlated to air temperature and increased in June and July when maximum temperature was approximately 30°C. In June 2003, we conducted a preliminary laboratory study to investigate the effects of desiccation on surf smelt egg mortality. Eggs were randomly placed into four relative humidity (RH) groups: dry (62% RH), moist (80% RH), wet (93% RH) and submerged (100% RH). All eggs in the dry and moist group died by the end of the experiment. Mortality of eggs in the wet and submerged groups was not significantly different (P<0.05). Eggs in the wet group reached the eyed stage and hatched significantly faster (P<0.05) than those in the submerged group. Results suggested a threshold RH requirement of 80 – 93% for successful development and hatching of surf smelt embryos. Moisture and temperature interact to condition RH in the intertidal zone. Shade vegetation, which can cool air temperature in the supralittoral zone, may be important for some populations of surf smelt. Further investigations are required to confirm the findings.