Health effects of pesticide among vinylhouse workers in Sangjoo County, Kyungpook Province were assessed by measuring cholinesterase, glutathion reductase, and methemoglobin. Activities of cholinesterases among vinylhouse workers and general farmers were 3.89U and 3.98U in serum and 5.29U and 5.50U in red blood cells, respectively. While levels of methemoglobin between vinylhouse workers(0.16%) and general farmers(0.17%) were very similar, glutathione reductase among vinylhouse workers were 8% lower than that of general farmers. Inhibition of RBC cholinesterase among vinylhouse workers was two times greater than general farmers, suggesting a greater exposure of vinylhouse workers to the organophosphate pesticides. Methemoglobin level among vinylhouse workers with more than or equal to 10 vinylhouse units was 13% higher than that of the workers with less than 10 units. Vinylhouse workers using protective gears during pesticide spray showed higher level of reduced glutathione and lower level of methemoglobin, as compared to the non-users. This indicates that protective gears play an important role against pesticide exposure. Vinylhouse workers practicing good personal hygiene showed a higher level of reduced glutathione, as compared to those with poor personal hygiene, indicating that personal hygiene is also an important factor in reducing pesticide exposure. The present study represents a first attempt to analyze cholinesterase, methemoglobin and glutathione reductase activities among the vinylhouse workers. While neither vinylhouse workers nor general farmers showed abnormal findings among biochemical parameters used in the present study, increased level of methemoglobin and decrease of glutathione reductase activity among vinylhouse workers suggest that these workers have been subject to a higher exposure of pesticide than general farmers.