Chromosomal and cross-mating studies were used to study populations of Anopheles farauti Lav. in Australia. The results indicate that the 2 cryptic species called A. farauti No. 1 and No. 2 [see RAE/B 60, 1868; 61, 1456, etc.] are both present in Australia. In addition, evidence is presented that a third biological species is present in sympatry with them in Australia. Difficulties in identification, and the relevance of these findings, are discussed.