Methods and compositions for identifying novel pesticidal gene homologues are provided. Specifically, the methods of the invention comprise systematically designing oligonucleotide primers that are specific for a pesticidal gene of interest and performing successive rounds of PCR amplification of nucleic acid material from a microorganism, particularly a Bacillus thuringiensis strain, to identify novel homologues of known pesticidal genes. Oligonucleotide primers that can be used to practice the present methods are further disclosed.