RESUMEN
There is a case of a couple who intentionally killed their children with methomyl insecticide. This was presented as our initial investigation of plasma cholinesterase (ChE) activity in Thai children. A hundred and five healthy Thai children 5-6 years of age, participated in the project. Their plasma was drawn to measure ChE activity. Mean +/- standard deviation of the children ChE was 7,417 +/- 1,620 U/L. The enzyme activity of the children was not significantly different between gender and parents' occupations. However, the mean of female ChE activity appeared to be lower than male ChE. Children whose parents were farmers appeared to have lower ChE activity than those whose parents were employees, merchants, government officers, unemployed parents, or private business owners. Two victims of child homicide were presented with ChE activity approximately 6 and 9 per cent of the average, considering healthy children. It was concluded that children's plasma ChE activity lower than 10 per cent of normal, could be a lethal indicator of anti-ChE insecticide poisoning.