People who exhibit the type A behaviour pattern have different approaches to problems compared with their non-type A counterparts. On the basis of published work on such differences, a number of predictions were tested in 85 outpatients with type I diabetes. Contrary to expectations, no differences were observed in glycaemic control between type A and non-type A diabetics of either sex. However, dividing type A diabetics according to their health locus of control beliefs yielded significantly different groups in terms of glycaemic control.