The stock structure of the exploitable population of striped bass Morone saxatilis in Rhode Island coastal waters was estimated by a quadratic discriminant analysis of nine proteins of eye lenses separated by isoelectric focusing. This technique permitted identification of Hudson River and Chesapeake Bay striped bass with 88.0 and 89.5% correct classification, respectively. Classification of individuals sampled from the Rhode Island commercial trap-net fishery in November 1982 indicated that approximately 54% were from the Chesapeake Bay stock and 46% were from the Hudson River stock. These stock composition estimates apply to age-2–5 striped bass from the exploitable population in Rhode Island. The stock composition of the coastal population is expected to change with time and with relative year-class strengths of the contributing stocks.