Abnormalities of immune status, particularly a high prevalence (about 50%) of thyroid autoantibodies, have been reported before in Turner syndrome. Results are conflicting as regards other abnormalities of immune fuction. Growth hormone (GH) has immunomodulatory effects, but results of its effects on GH-deficient children are inconsistent. In this study, 42 girls with Turner syndrome, aged 7.3-19 years, are investigated before, during and after 4 years of human GH therapy. Girls over 12 years old also received ethinyl oestradiol. The prevalence of antithyroid antibodies was 16.7% initially, 35.3% after 24-45 months and 48% after 4 years of therapy though, as there was no control group, it was difficult to conclude that GH was enhancing their appearance. Hypothyroidism was extremely uncommon, and the growth response was no different in those who had the antibodies from those who had not. There were no dramatic increases in prevalence of any of the other antibodies investigated, though the prevalence of parietal cell antibodies was higher than expected.