The Random Amplified Polymorphic DNA (RAPD) technique was used to develop molecular markers linked to sex expression in Pistacia vera, a dioecious species. Progenies from two female parents (`Lassen' and `Kerman') pollinated by a common male parent (`Peters') were studied. Two bulks of DNA were made in each cross, one from males and one from females. DNA was extracted from each bulked sample as well as from each of the contributing individuals and from 14 additional P. vera cultivars. Twelve hundred decamer oligonucleotide primers were used to perform DNA amplification on the bulk DNA. This analysis led to the identification of one primer (OPO08) that produces a 945 bp. amplification band present only in females and absent in males. The relationship between band presence and female sex expression was conserved in every individual obtained from the two crosses and in 14 cultivars unrelated to the crosses. This band, which we propose is tightly linked to the gene(s) controlling sex determination, provides a reliable marker for sex of pistachio seedlings and should be a useful tool in pistachio breeding.