A mean body mass index (BMI) of 25.4 +/- 5.0 kg/m(2) was calculated in 15439 euthyroid patients newly referred to our thyroid outpatient department from January 1, 1992 until December 31, 1999. This patient population included 2916 men aged 50 +/- 16 years (BMI: 26.2 +/- 4.3 kg/m(2)) and 12563 women aged 47 +/- 17 years (BMI 25.3 +/- 5.1 kg/m(2) ). Mean BMI appeared to rise (p < 0.01) from 25.0 +/- 4.7 kg/m(2) (1992) to 25.6 +/- 5.0 kg/m(2) (1999) and the share of obese patients (BMI > 30 kg/m(2)) increased from 13.8% in 1992 to 17.2% in 1999. However these changes were parallelled by a rise (p < 0.01) in the mean age of newly referred patients from 45 +/- 16 years (1992) to 49 +/- 17 years (1999). When the whole population was subdivided into groups of different age no time-related trend was apparent in mean BMI or in the prevalence of obesity in any of these subgroups. Only in men and women beyond 60 years of age BMI of those referred in 1998 and 1999 was higher (p < 0.05) than in those individuals referred in 1992-1994. These data indicate that close to half of all euthyroid patients referred to a thyroid outpatient service in eastern Austria is overweight. From 1992 to the end of 1999 there was, however, no marked increase in the prevalence of obesity in this population.