Optimal regimen for insulin therapy should lead to normal longitudinal growth and weight gain in children with diabetes mellitus. However, reports published so far indicate that this goal of paediatric diabetology is currently not achieved in a considerable number of patients. In a cross-sectional sample of 89 children with insulin dependent diabetes mellitus (IDDM) for more than 3 years, we found the relation of height to weight to be significantly different compared to 102 healthy school children of similar age. Using bivariate analysis, body shape in these children with diabetes was shifted towards small and obese (P less than 0.05) compared to control children. We subsequently initiated a longitudinal study and followed children from the onset of diabetes for the following 3 years, recording height, weight and bone age as well as glycosylated haemoglobin and daily insulin requirement. At diagnosis, height SDS was identical in children with IDDM (+0.04 +/- 0.10) compared to control children (-0.07 +/- 0.10; M +/- SE), while weight SDS was -0.26 +/- 0.10 in children with diabetes (controls: + 0.01 +/- 0.01). Bone age was identically retarded in newly diagnosed IDDM children (-0.73 +/- 0.12 SDS) and in our control group of children from the same regional background (-0.50 +/- 0.12; n.s.). In this group of children with diabetes mellitus followed prospectively, height to weight relationship differed from controls after 2 and after 3 years of the disease (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)