Discriminant function analysis was made of morphometric data from laboratory stocks of Anopheles dirus species A (Thailand), species B (Perlis, Malaysia) and material from natural populations of a third species here designated An. balabacensis sensu stricto from Sabah which differ in their polytene chromosomes. The results showed that discrimination of all three types was successful for both larvae and pupae. The significance of these findings are discussed with consideration of their practical implications for those taxa which include individuals of public health importance.