Tanytarsus dissimilis (Johannsen) was exposed to four heavy metals. Static exposure began during embryogenesis and continued through hatching and larval development to the 2nd or 3rd instar. The LC50 concentrations for cadmium, copper, and zinc were 3.8, 16.3, and 36.8 micrograms/l. The LC50 for lead was 258 microgram/l. Growth was not reduced at exposure concentrations less than the LC50. The LC50 concentrations obtained in this insect exposure are as much as 1,600 times lower than other insect exposures reported in the literature. This is probably due to a combination of exposure of this insect during important life cycle events and species-specificity.