Numerous Virgin Islands plants have become rare or extinct over the last 200 years due to cultivation, development, and introduction of exotic species. St. John endemic Solanum conocarpum (Solanaceae) has fewer than 200 known individuals currently extant in the wild. DNA fingerprinting with RAPD PCR was used to assess the population genetics of S. conocarpum and congener S. polygamum. In addition, controlled crosses were performed to determine whether the plant was self-incompatible. Finally, seedlings were outplanted and monitored to (1) restore small populations and (2) compare performance of individuals from the largest and smallest populations of the species. Population genetic analysis revealed that species level diversity in S. conocarpum remains high, but that virtually all diversity is confined to a single population. The crosses performed indicated that the species is completely selfincompatible. While seedlings from the smallest population performed poorly in the greenhouse by comparison with plants from the large population with higher genetic diversity, both groups performed equally well in the field over a three-year period. The species' high level of overall diversity and ability to survive even when diversity is reduced suggest that prospects for conservation are good. In order to ensure the survival of the species, all populations should be brought up to sizes large enough to allow outcrossing, and ex-situ conservation should be employed.