In line with Jean Piaget’s conservation concepts and Lawrence Kohlberg’s work on gender constancy, a study was conducted among Filipino preschoolers to determine the development of their gender constancy and determine the relationship between gender constancy and genital knowledge. Age and gender differences were also determined. The 87 preschoolers, aged 3-5 years old, from three laboratory schools completed the following tests: the Own-gender constancy test, Other-Gender Con- stancy test, and the Genital Knowledge test. For own-gender constancy, sex was a significant variable. The mean score of male preschoolers was higher than female preschoolers. For other-gender constancy, age was a significant variable. There was a difference in mean scores across the three age groups. There was a positive but low correlation between own-gender constancy scores and other-gender constancy scores. This relationship was also observed for other-gender constancy and genital knowl- edge.