Proteins associated with 36S virus RNA from Vero cells infected with San Miguel sea lion virus, type 2 (SMSV-2), were labelled with 125I. One protein, VPg, remained linked to RNA when subjected to deproteinization techniques. VPg labelled wtih 32P was observed on 36S RNA from purified virions; the quantity of label was compatible with two phosphates per genome. The estimated mol. wt. of SMSV-2 VPg was 15 000.