Abstract: Importance of neem products as insecticide, pesticides and herbicides is well recognized recently use of these products is insecticide in vegetables is being increased rapidly. Studies on seasonal incidence and effect of some neem products on Hadda beetle (Henosepilachna vigintioctopunctata fabr.) infested on Brinjal (Solanum melongena L.) were conducted at Allahabad Agricultural Institute-Deemed University, Allahabad during Rabi season 2006. The treatments of some commercial neem products viz. Neem Raj, Neemoria, Neem bark, Garlic, Neem Gold, Neem Seed Kernel Extract (NSKE), Neem leaf, Achook and one insecticide, i.e., Endosulfan were applied. The observation pertaining to the population of Hadda beetle on brinjal were recorded one day before treatments; the observation on the population mortality were recorded at 1, 2 and 5 days after treatments. The beetle population appeared in the 1st week of March (10th standard week) with an average population level of 0.1 beetle/leaf. Hadda beetle population gradually increased and reached peak level of 3.64 per leaf upto 3rd week of April (16th standard week). However, the population declined with maturation of the crop. Endosulfan was the most effective treatment with 100% mortality. All the other treatments were also effective at 5 days after spraying and they were also statistically at par with each other. Declined of beetle population was not much dependent on weather parameters (temperature, wind velocity, rainfall and relative humidity) but was influenced by the maturation of crop. The present study recommends that Endosulfan (0.07%) as the most effective treatment to control Hadda beetle infestation in Brinjal.