The presence of some guava (Psidium guajava L.) trees possessing white fruit pulp, scattered in a 30,000 tree-orchord (Fábrica Peixe, Santo Antônio da Posse, São Paulo) bearing red pulped fruits, was recorded. Since white pulp is recessive to red pulp, the existence of those trees afforded the opportunity of using the gene responsible for the first character as a recessive marker in studies of cross pollination Three fruits of open pollinated flowers were collected from each plant possessing the recessive gene and the seeds obtained were sown. When the trees arising from such seed bore fruits, the number of plants with red or white pulped fruits was determined (table 1) and these data were submitted to the chisquare test of homogeneity of proportions. The results obtained indicated that the amount of cross pollination varied from plant to plant, ranging from 25.7% to 41.3% (table 2). It is considered that the mean value obtained, 35.6% is a good approximation of the true value of cross pollination in guava. According to the literature, the main pollination agent for this plant is the common bee (Apis mellifera L.).