Objective: The current research was designed to develop a health education programme for type 2 diabetes mellitus based on the Taba-Tyler model and to evaluate its effect. Design: The study was quasi-experimental in design. Setting: Fifty-five patients from the Endocrinology and Metabolism Unit, University Hospital of Ankara. Method: An education programme was developed on the basis of the Taba-Tyler model. Subjects received two educational sequential forty-minute sessions. The objectives of the education programme covered knowledge about type 2 diabetes mellitus. To assess the effect of the programme, a test was developed which was applied at the beginning and at the end of each session. The mean of the correct answers of pre- and post-tests were analysed to assess the effect of the programme. The results were also analysed across the independent variables demographic and medical characteristics. Results: In every content area, the percentage of correct answers increased approximately from 45.0 per cent to 75.0 per cent. The score of pre-test was 11.7 [plus or minus] 4.7 and the score of post-test was 17.8 [plus or minus] 3.5. The difference between two scores was statistically significant. Independent variables such as employment status and having a family history of diabetes, influenced the level of knowledge of diabetes ("p less than 0.05"). Conclusion: This study reported a change in knowledge, but no evidence was collected to determine whether any behaviour changes occurred.