1. Polyacrylamide gel electrophoresis (PAGE) in 4% gels of Blatta orientalis larval hemolymph revealed 4 major proteins. 2. Maximum incorporation of [14C]-leucine into total hemolymph protein occurs within 24 hr and is followed by negligible turnover in the next 24 hr. 3. Quantitative PAGE was used to monitor concentration changes during the molting cycle in synchronously molting cultures. 4. All 4 proteins show the same temporal rhythm of variation but different amplitudes. 5. The widely differing concentrations achieved are accounted for by different rates of synthesis.