This study aimed to find relationship between length of exposure of organophosphate pesticides with cholinesterase enzyme activity in the farmers’ blood. The study was conducted at the Joint Farmers Group in Kelurahan Campang year 2009 using crosssectional study design and sampling by the simple random sampling method (56 respondents). Data collection was carried out by interview and blood cholinesterase was measured using the Livibond Cholinesterase Test Kit AF267. Results showed that 100% farmers were poisoned, with 71.4% suffer from light-over-exposure and 28.6% moderateover exposure. Bivariate test analysis using chi-square test showed that there are no statistically significant relationship between the length of exposure (year of working as pesticide farmer, spraying time per week, and the last time spraying) with poisoning level (over-exposure probable and serious-over exposure). It takes the role of government to educate and trained farmers how to use pesticide safely and the importance of personal protective equipment to reduce the poisoning level.