Abstract. In this report we show that Drosophila melanogaster muscles contain the standard form of the thick filament protein paramyosin, as well as a novel paramyosin isoform, which we call miniparamyosin . We have isolated Drosophila paramyosin using previously established methods. This protein is =105 kD and cross-reacts with polyclonal antibodies made against Caenorhabditis elegans or Heliocopris dilloni paramyosin. The Heliocopris antibody also cross-reacts with a