OBJECTIVES: To investigate: (i) the incidence of impaired fasting glycaemia (IFG) developed over 5 y in a population-based sample of Australian-born women; (ii) prospectively the factors which are associated with the development of IFG; (iii) the association of the menopausal transition with the onset of IFG and an increase in serum insulin concentrations. DESIGN AND METHODS: A total of 265 women (110 pre-, 138 peri-, 17 postmenopausal) participants in the longitudinal phase of the Melbourne Women's Midlife Health Project, aged 46-57 and with normal fasting plasma glucose concentrations at the time of the initial measure, were interviewed, had physical measurements and blood taken annually over a 5 y follow-up period. RESULTS: During the study period 43 women (16%) recorded a fasting glucose concentration of > or =6.1 mmol/l (IFG). Women who recorded IFG prospectively had, at the time of the initial measure when fasting glucose concentrations were normal: higher body mass index (BMI), trunk skinfold thicknesses, waist and hip circumferences (P<0.005), lower SHBG, higher free androgen index and serum insulin concentrations (P<0.05), higher systolic blood pressure, serum triglyceride and lower HDL-cholesterol concentrations (P<0.05) than women whose fasting glucose concentrations remained normal. The onset of IFG was not triggered by the menopausal transition or hormone use. Changes in insulin concentration were associated with changes in BMI (P<0.05). CONCLUSION: Women who developed IFG during the menopausal transition exhibited significantly higher levels of body fatness and dyslipidemia, premenopausally, compared with the women who did not develop IFG. The menopausal transition did not have an effect on the development of IFG, but weight gain during this period was associated with an increase in insulin concentration.