Studies on effect of varying levels of nitrogen, phosphorus and potassium on flowering, fruit set and sex ratio of cucumber showed that, nitrogen levels had a significant effect on number of days required for initiation of first male and female flowers, number of male and female flowers per vine, number of days required for frist furit set, fruit set per cent and sex ratio during 2001 and 2002. Phosphorus levels also showed positive effect on number of male and female flowers per vine, fruit set per cent and sex ratio. Whereas, application of varying levels of potassium had no significant effect on flowering, fruit set per cent and sex ratio of cucumber cv. Poinsette during both the years.