Effects of salinity on the survival, growth, and development of stable fly, Stomoxys calcitrans (L.), were investigated in the laboratory. Larvae failed to develop to pupation when reared in media containing a salinity of 40 parts per thousand (ppt) sodium chloride (NaCl). Maximum salinity supporting larval development equaled the salinity of seawater (34 ppt); the larval LC90 was 24.2 ppt. Deleterious effects of high salinity decreased as larvae matured. Six-day-old larvae reared at a salinity of 34 ppt weighed 79% less than controls, compared with a 36% difference in 9-d-old larvae; by pupation, the difference was only 24%. Salinity did not influence the duration of larval, pupal, or adult stages. Survival of pupae was unimpaired despite a slight increase in number of pupal deformities, and normal adults emerged. Eggs were highly tolerant to saline. They hatched at salinity concentrations lethal to larvae; greater than 50% hatch occurred even when eggs were maintained at 80 ppt NaCl. Sensitivity of larvae to salinities close to that of seawater might be important for control of stable flies inhabiting marine areas.