Two molecular techniques which reveal highly variable DNA polymorphisms, RAPD and multilocus DNA fingerprinting, were used to evaluate genetic diversity between six aquacultural strains of Oreochromis niloticus (tilapia) from the Philippines. The results using both techniques were in close agreement Within-strain heterozygosity values were similar and were correlated between the two data sets, but statistical errors associated with the RAPD data set were lower. Although genetic distances between strains were greater using DNA fingerprinting, the distances measured using both methods were significantly correlated. Both methods were useful in estimating variation between strains, but they offered different advantages. RAPD was technically easier to perform and produced results with low statistical error, whereas DNA fingerprinting detected greater genetic differentiation between strains. The theoretical basis for using RAPD and multilocus minisatellite markers for population studies is discussed.