Knock-down and mortality were measured using WHO cone tests for adult mosquitoes (Anonymous WHO, 1998). The tests were conducted using the standard WHO plastic cones and a three minute exposure time. Five non blood-fed females two to five days old were introduced into the cones at a time. Four cones were applied at the same time onto the net sample and tests were carried out at 25° C ± 2 under subdued light. After exposure, the females were grouped into batches of 10 in 150 ml plastic cups and maintained at 27° C ± 2 and 80 % ± 10 RH with a honey solution provided. For each sample tested, 50 mosquitoes (ten cones) were used. Knock down rates were recorded after exposure at fixed intervals of time (every two to 10 min depending on KD rates) up to 60 min after exposure. KDT50 and KDT9 5 with 95 % confidence limits were calculated using log-probit analysis. Percentage mortalities were recorded after 24 h and compared by a Chi square test. All tests were replicated two to three times on different mosquito batches and conducted in parallel with a control where no insecticide was applied to the net. The results were corrected accordingly to Abbott (1925) when mortality in the control was above 5 %.