We determined how frequently multiple mating occurs in a field population of Anopheles freeborni Aitken. We used enzyme electrophoresis to analyse field collected females and their offspring, and determined the parity rates of females mating in swarms. The genotypes of progeny in one of the 36 families examined showed conclusive evidence of two sires. 4·3% (n═93) of females mating in swarms were parous, as opposed to 33·9% of host seeking females (n═103). We conclude that multiple mating in A. freeborni occurs at low frequency in the field, and may be ascribed to incomplete transfer of sperm or male accessory gland substance, rather than to routine renewal of receptivity by females.