Genomic DNA was extracted from Schistosoma mansoni adult worms and deliberately degraded by sonication. Samples with varying average molecular weight were subjected to RAPD (randomly amplified polymorphic DNA) analysis using the primer 3307 (5'-AGTGCTACGT-3') and other primers. Reproducible and complex DNA banding patterns were obtained, irrespective of the extent of DNA degradation. The same amplification protocol was employed with naturally degraded Biomphalaria glabrata genomic DNA and the primer 3302 (5'-CTGATGCTAC-3'). Again, reproducible RAPD patterns resulted. The experiment shows that the partially degraded DNA samples can be safely compared in RAPD analysis without artifactual bands compromising the accuracy of genetic analysis. Thus RAPD analysis permits complex and reproducible DNA fingerprinting from degraded samples of parasitological interest.