This study aimed to measure the prevalence of twins among all conceptions and to identify demographic factors for twinning in Pattani province of southern Thailand. The sex distribution of the twins was also investigated. Data on demographics and reproductive history of the mother were obtained from Pattani Provincial Hospital. From 1 October 1996 to 30 September 2005, 22,906 infants including 221 twin pairs were delivered to 19,126 mothers on 22,685 occasions. Triplets (4 occasions) and referral mothers (3,433 occasions) were excluded from this study. The prevalence of twins was 9.7 per 1,000. Based on the fact that 186 of these pairs were of the same sex, the estimated proportion of identical twins was found to be 0.68 (95% CI: 0.59-0.78). After preliminary analysis of demographic factors, logistic regression was used to model prevalence. The only statistically significant determinants of twinning found were the mother's age and religion. No associations were found between the sex distribution of the twins and any demographic factors. A more extensive study would need to be done to examine possible associations between prevalence of same-sex twins and ethnic factors in the region.