The objectives were to describe chemical use among farmers; to develop an exposure intensity score for three chemicals of interest: organophosphates (OPs), glyphosate (GP), and phenoxy herbicides (PHs). This was a cross-sectional study of a stratified random sample of farmers. Demographic, health and chemical use information were collected via questionnaire and an exposure level score developed. Within a sample of 586 farmers, 16 - 54% applied one or more of the chemicals. A high proportion of pastoral farmers used all the chemical types with 65% applying GP, 29% OPs and 19% PHs. Mean exposure scores were higher among women OP users, younger PH users, and arable farmers using PHs. This pesticide exposure score based on self-reported work practices among farmers can give an estimate of comparative annual exposure level. It can be used in analytical epidemiological studies and allows the identification of priority areas for intervention.