Monitoring of insect population in the field is one of the essential components in the integrated pest management programs. So, an experiment was carried out at Sakha Agric. Res. Station Farm, Kafr Fl-Sheikh to monitor the population of leafhoppers in cotton fields using two sampling methods (direct count on cotton leaves and sweeping net) as well as effect of some prevailing climatic factors on the population density during two successive growing seasons, 1999 and 2000. The results obtained indicated that the numbers of leafhopper nymphs found by direct count were more than adults, while the reverse occurred in sweeping net samples. The highest population of leafhoppers occurred during June, July and August and there was insignificant variation in the population density between the two study seasons. The adults of leafhoppers were more affected by the three considered factors (temperature, relative humidity and wind speed) than nymphs in the two seasons and the temperature was the most important factor affecting the population.Thus, the direct count sampling method should be used for estimating leafhoppers population when the integrated insect management programs are applied in cotton fields.