Sodiumdodecylsulphate (SDS)-solubilized proteins of several developmental stages of Dipetalonema viteae (adults, uterus content, microfilariae, infective larvae) were subjected to SDS-polyacrylamide gel electrophoresis and transferred onto nitrocellulose filter sheets. Their antigenicity in natural infections of Meriones unguiculatus was investigated by immuno-recognition with pooled sera of infected hosts. The antibodies were labelled by radioiodinated protein A and visualized by autoradiography. Immunorecognized protein bands were demonstrable in all stages, some of them being stage specific, others common to several or all stages. The highest number of labelled protein bands was found in extracts of adult worms, the lowest in preparations of microfilariae and infective larvae.