Sulphatide is a newly described autoantigen in insulin-dependent diabetes mellitus; it is present in the islets of Langerhans, and anti-sulphatide antibodies are found in diabetic patients and in spontaneously diabetic BB rats. The aim of the study was to treat neonatal BB rats with sulphatide in order to induce tolerance and thereby possibly influence later diabetes development. One hundred and twelve newborn BB rats, divided into three groups, were treated once daily during the first 6 days of life with intrathymic injections of sulphatide, galactosyl-ceramide (which is similar to sulphatide but without sulphate) or phosphate buffer alone. Although the results showed no difference in diabetes incidence among the three groups, there was a delayed onset of diabetes in the sulphatide-treated group, which developed diabetes on average at 77 +/- 1 days of age, compared to 70 +/- 2 days (p < 0.02) for the galactosyl-ceramide-treated group and 70 +/- 1 days (p < 0.01) for the buffer-treated group. The degree of insulitis and the size of islets of Langerhans were studied histologically for the diabetic animals in all three groups; there were no significant differences although the sulphatide-treated group tended to have a more normal histology. The blood glucose levels for the diabetic BB rats were similar in all three groups. Thus, neonatal treatment with the diabetic autoantigen sulphatide at the chosen dosage does not influence the incidence of diabetes, but delays the onset of disease.