The mechanism of dopamine-induced inhibition of hemoglobin synthesis in chick blastoderm in vitro was investigated. Dopamine did not reduce the incorporation of 14C-leucine or 14C-aminolevulinic acid (ALA) into protein. The total protein per blastoderm was similar in both the dopamine-treated and control blastoderms. Addition of exogenous ALA to the dopamine-treated medium did not reverse the effect of dopamine on hemoglobin synthesis.