Genetic variation of nine upland and four lowland rice cultivars (Oryza sativa L.) was investigated at the DNA level using the randomly amplified polymorphic DNA (RAPD) method via the polymerase chain reaction (PCR). Forty-two random primers were used to amplify DNA segments and 260 PCR products were obtained. The results of agarosegel electrophoretic analysis of these PCR products indicated that 208 (80%) were polymorphic. All 42 primers used in this experiment were amplified and typically generated one-to-four major bands. Only two primers showed no polymorphisms. In general, a higher level of polymorphism was found between japonica and indica subspecies while fewer polymorphisms were found between upland and lowland cultivars within the indica subspecies. A dendrogram that shows the genetic distances of 13 rice cultivars was constructed based on their DNA polymorphisms. Classification of rice cultivars based on the results from the RAPD analysis was identical to the previous classification based on isozyme analysis. This study demonstrated that RAPD analysis is a useful tool in determining the genetic relationships among rice cultivars.