An outbreak of Plasmodium vivax malaria occurred in Trinidad some 25 years after a successful eradication programme. The 'index case' was infected while visiting Perdaneles, Venezuela, and was responsible for the renewal of malaria transmission by indigenous Anopheles aquasalis mosquitoes in Icacos, Trinidad, W.I. Nine cases (four females and five males) of P. vivax malaria were locally transmitted in Icacos. Most of the cases (70%) were in the 15-24 or 25-44 year age groups. In Granville/Chatham, another, unrelated case of locally transmitted P. vivax malaria was discovered through active surveillance. The intervention measures adopted, which successfully eradicated P. vivax malaria from Trinidad, are described. The need to maintain malaria surveillance is emphasized.