On three islands of the Seychelles archipelago, the baculovirus of Oryctes rhinoceros was introduced into populations of Oryctes monoceros and became established. The percentage of infected beetles fluctuated between 20 and 50 and a modest population reduction (ca. 30%) was recorded. On a separate group of islands (Praslin group) the virus was found to have survived from a previous release made in 1973; on these islands the rate of infection was between 70 and 90%.