The present work was carried out at El-Wasta district, Beni-Suef governorate, during 1999 & 2000 cotton seasons, to study the population fluctuation of certain sucking pests and their associated natural enemies with interrelations between them.

Obtained data showed that the population fluctuation of common red spider mite Tetranychus arabicus Attiah, thrips, Thrips tabaci (lind), aphid, Aphis gossypii Glover and whitefly, Bemisia tabaci (Genn.) and their associated natural enemies of insects, mites and true spiders as well as the effect of temperature and relative humidity.

Results obtained could be summarized as follow:-1. In both seasons the population of common red spider mite T. arabicus has two peaks of abundance during seedling and bolling stages. Climatic factors affected positively mite population.
2. The infestation with cotton thrips Thrips tabaci started heavily as soon as the cotton seedlings appeared (20-25 days after planting).
3. The population of cotton aphids Aphis gossypii recorded three small peaks during seedlings and bolling stages. Meanwhile the abundance of whitefly regarding two distinct peaks occurred during August of 1999 & 2000 seasons.

The statistical analysis of obtained data showed that non-significant correlation coefficient found between the populations of certain sucking pests infesting cotton and their natural enemies except that of spider mites, correlation was generally negative while it was positive for whitefly.