The population densities of the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) were observed in a pesticide-free cotton field in Egypt. The highest population density of was noted in September, whereas the lowest was noted in June. The plant's central section indicated the maximum population density, whereas the plant's top section indicated the lowest population density. The population density of mites found on the undersides of the leaves was significantly higher than that of mites found on the upper sides of the leaves. The bases and pleats of the undersides of the leaves harboured the mite majority. Neither Lambda cyhalothrin (5%) E.C. nor Chlorpyrifos methyl (48%) E.C. had a significant effect on the mite numbers. A defoliant was sprayed in the pesticide-free area. A week later, the recently fallen leaves had the greatest mite population density. A few recently fallen leaves were collected from an area treated with both defoliant and the two pesticides. When they were stacked in a glass jar covered with opaque fabric apart from the opening, in a continuously lit laboratory, the majority of the mites congregated on the topmost leaves.