Successful results in preparing chromosome specimens of Culex pipiens complex were obtained by modifying the methods reported for Drosophila and Anopheles. For preparation of the salivary gland chromosomes, 4th instar larvae were dissected in 0.1% solution of sodium oxalate and the glands were isolated from between head and thorax, soaked in freshly prepared fixative for two minutes, stained in 2% orcein solution in the equal amount of the mixture of 85% lactic acid and acetic acid glacial for 3 to 4 minutes, rinsed with the acetic acid and lactic acid mixture, and were squashed under a cover-glass with adequate pressure of a finger. The fixative was prepared by mixing 25 parts of 85% ethanol, 23 parts of 50% acetic acid, one part of 11% formaline and 25 parts of distilled water. Materials of ovaries were prepared by dissecting either 4th instar larvae or pupae at the joint between 6th and 7th abdominal segments, while those used for the study of testes were obtained from pupae since larval testes were immature and too small. Similar techniques as above were applied for the preparation of reproductive organs, but the organs isolated in 0.1% solium oxalate solution were transferred directly into the stain without treating in the fixative.