In the early 17th century, male servant eunuchs were common, notably at the Persianised Acehnese court of Iskandar Muda. By the mid-eighteenth century, the castration of male slaves mysteriously disappeared. Concubinage, however, lasted much longer. While there were sporadic attempts to stamp out abuses, for example sexual relations with pre-pubescent slave girls, and possibly, clitoridectomy, a reasoned rejection of the institution of concubinage on religious grounds failed to emerge. This paper discusses the sexual treatment of slaves across Islamic Southeast Asia, a subject which sheds important light on historical specificities pertaining to both Islam and sexuality in the region, yet which continues to be treated with silence, embarrassment or even scholarly condemnation.