Marituba virus was purified by rate-zonal sedimentation and equilibrium density centrifugation in sucrose gradients. The buoyant density of virus particles was 1.19 g/ml. Purified virus was dissociated and its proteins were analyzed by SDS-PAGE. Four virus polypeptides were identified and designated L, G1, G2 and N. Their average molecular weights were 190 x 10(3) [L, range (180-200) x 10(3)], 120 x 10(3) [G1, range (118-122) x 10(3)], 26 x 10(3) [G2, range (24-28) x 10(3)], and 20 x 10(3) [N, range (19-21) x 10(3)]. Polypeptides N and L are, respectively, the major and the minor viral components. G1 and G2 are glycopeptides as demonstrated by the preferential incorporation of labeled 3H-glucosamine.