British law provides for the prosecution of so-called "sex tourists," as it makes it an offense to commit sexual offenses against children in another country. It is unlawful under British law to have sexual intercourse with a girl under 13 years old. The current study involved a literature review for the purpose of aiding in the determination of age of girls from images of intercourse that involve young Southeast Asian girls from countries where "sex tourism" is promoted. Although there are limited data on the age of menarche (first menstrual period) from the countries at risk of "sex tourism," a recent Philippines study indicated that the mean age of menarche was similar to the mean age of British girls born between 1982 and 1986. There are no data for these countries on the early pubertal changes in breast development, but studies from India and China have suggested that these might be more prolonged than for British girls. The interval between early pubertal breast development and menarche was nearly 3 years in these developing countries, compared with 2 years for the British girls. Maternal malnutrition and girls small for gestational age at birth resulted in an earlier menarche, and chronic malnutrition sufficiently severe to cause stunting in preschool years caused a delay in menarche. Based on information from existing studies, the authors estimated that 97.5 percent of Southeast Asian girls will show pubertal changes of early breast development by the age of 13.7 years. They conclude that pediatricians might be able to give a relatively accurate expert opinion only in cases of prepubertal girls involved in sex tourism. In cases of girls in early puberty, this review cannot provide answers; detailed studies in the affected countries are required. 3 tables and 22 references