Piper longum L., a medicinally important plant, showing a dioecious flowering pattern - plants bearing either male or female sex organs - was investigated for the molecular basis of genotypic differentiation between the male and female plants, using randomly amplified polymorphic DNA (RAPD) technique. Polymorphism in the genomic DNA of plants of twenty-five female and six males was analysed by RAPD, using 40 decamer random oligonucleotide primers. Two RAPD bands consistently appeared only in the plants showing male genotype, suggesting thereby the male-associated nature of these DNA markers in dioecious P. longum. So far, in this wild species of Piper, genetic or chromosomal basis of dioecy has not been reported. Perhaps, this is the first report- to the best of our information - on male-associated RAPD markers in P. longum.