ninaED1, a dominant allele of the major Drosophila rhodopsin gene, expresses a rhodopsin that is predominantly recovered in a 80-kD complex that likely represents rhodopsin dimers. By driving either ninaED1 or ninaE+ expression from a heat-shock promoter, we show that the 80-kD rhodopsin complex forms immediately after gene activation. In wild type, but not ninaED1, rhodopsin monomeric forms are detected at later times. The generation of monomeric forms of wild-type rhodopsin is suppressed in vitamin A-deprived flies or in flies heterozygous for the dominant rhodopsin mutation. We also show that ninaED1 expression does not affect the maturation of another Drosophila visual pigment, Rh3. These results are consistent with the view that the ninaED1 rhodopsin antagonizes an early posttranslation process that is specific for maturation of the ninaE-encoded rhodopsin.