Protostelids, dictyostelids and myxomycetes are well known from terrestrial ecosystems in temperate regions but poorly known from the tropics. This study examined the distribution and ecology of these three groups of ‘slime moulds’ in the forest floor litter microhabitat of five different forest types (tabonuco forest, secondary tabonuco forest, palo colorado forest, palm forest, and elfin forest) within the Luquillo Experimental Forest in Puerto Rico. Protostelids associated with aerial litter (dead but still attached plant parts) also were studied. At least 13 species of protostelids, 13 species of dictyostelids and 24 species of myxomycetes were recovered. Both species richness and abundance of dictyostelids and myxomycetes were higher in the secondary tabonuco forest than in any of the other forest types. The tabonuco forest yielded the most species of protostelids, but the next highest total was recorded from the secondary tabonuco forest. Both of these forest types are located at the low end of the elevation gradient. Lowest levels of species richness and abundance occurred in the elfin forest, located at the high end of the elevation gradient. The general pattern observed was that of decreasing diversity with increasing elevation.