Objective: To investigate the effects of a sex education programme designed for parents on their communication with their teenage children about sexual matters.

Type of research: Quasi-experiment

Materials and methods: The sample consisted of 40 parents and 40 of their teenage children divided between two groups; one from an urban school and the other from a rural school. The parents attended the education programme over two days and one evening. Data was collected before and after attending the programme then a follow-up study was made on the parent's frequency of communication about sex education with their teenage children by phone and a questionnaire sent by mail. The programme was tested for its content validity by three experts with reliability values of 0.80 and 0.83. The data was analysed using descriptive statistics and paired t-test

Results: The effects of the programme revealed that the levels of communication both before and after attending the programme were significantly different (p < 0.05) with the mean score for communication after attending being higher than before attending for all the tested aspects: communication about sex with teenage children; teenage physical development; teenage relationships with the opposite sex; HIV/AIDS prevention; unwanted pregnancy prevention; medical use by teenagers and teenagers' understanding about the role of men and women according to Thai social standards. The level of the parents' and teenagers' satisfaction towards sex education was high.