18 boys and 12 girls with diabetes (average duration of diabetes: 4.4 years, average age: 11.1 years with age at diagnosis: 5.9 years) were studied over a 3 year period. SM was measured on 3 or 4 occasions with chick-bioassay. GH was measured with a previously reported RIA method. All children were within normal range for height although the majority was below the 50% percentile. The average retardation in bone age was about 1 year. Average SM activity was for the group as a whole 0.87 ± 0.21 U/ml (normal range 1.0 ± 0.19 U/ml). This was not related to duration of diabetes, regulation or age at diagnosis. Children with long-standing diabetes or with diagnosis at time of puberty had SM values of 1.06 ± 0.28 U/ml and 1.15 ± 0.16 U/ml respectively, most likely related to pubertal growth. Low values were found in a newly diagnosed patient (0.30 U/ml) and in 3 patients with the most pronounced growth retardation (0.48 ± 0.10 U/ml). GH in urine was slightly increased in the group with long standing diabetes due to change in glomerulo-tubular function or increased secretion. If increased levels of GH persist this does not result in increased SM levels reflecting a central role of insulin in SM generation.