The 1,600 hectares of La Selva Biological Station are home to as many as 6,000-7,000 species of moths and butterflies-nearly half the number of Lepidoptera known for the entire North American continent north of Mexico. Knowledge of the moth and butterfly fauna of La Selva Biological Station exceeds that of any other comparable rainforest in the New World. Richness tallies for all but Gelechioidea, Pyralidae, and Noctuidae are felt to be representative, even though species accumulation curves indicate that there is still much to be learned, especially for microlepidopteran families. Species accumulation tallies for gracillariids and zygaenoids are examined in detail. The La Selva fauna is contrasted with that of southern New England and rough estimates are suggested for the total lepidopteran richness at La Selva.