The effect of several isolates of entomogenous nematodes, Heterohabditis spp., from Puerto Rico was tested under laboratory conditions against larvae of Galleria mellonella, Cylas formicarius, Euscepes postfasciatus, and Cosmopolites sordidus. Five isolates demonstrated their capacity to kill the insect larvae. Isolate 2 was considered highly effective against all insects tested; isolates 14 and 27 caused high mortality rates to larvae of G. mellonella, E. postfasciatus and C. sordidus. Isolate 17 was effective against larvae of C. sordidus; isolate 18 against E. postfasciatus. The rest of the isolates tested varied greatly in their ability to kill the larvae of the insects used.