We investigated the relationship between sex hormone binding globulin (SHBG) and pubertal gynecomastia in 21 adolescents evaluated longitudinally. Thirteen patients were given tamoxifen treatment after grading according to the Nydick classification (group 1). Group 2 consisted of eight patients followed without treatment. Gynecomastia existed bilaterally in 15 patients. There was a statistically significant breast size reduction in both groups. There was a significant decrease in serum SHBG only in group 2. These findings suggest that serum SHBG is increased by tamoxifen treatment in male adolescents. There was a decrease in SHBG levels through the duration of follow up in patients who recovered with or without treatment. However, this decrease was statistically significant in the untreated group, but not in the tamoxifen treated group. In conclusion, we suggest that the pubertal fall in SHBG levels is attenuated by tamoxifen treatment given for pubertal gynecomastia since tamoxifen increases SHBG levels in male adolescents.