This study was designed to evaluate the relationship between digital clubbing and serum growth hormone (GH) level in patients with lung cancer. Forty primary cancer patients, who were diagnosed by various methods, were included in the study. Twenty of these patients had clubbing and the other 20 who did not and were considered as the control group. Serum GH levels were measured by radioimmunoassay. The normal serum values of GH were 0.1-6.5 ng.dL-1. None of the patients had a value over 6.5 ng.dL-1. The mean GH value of lung cancer patients with clubbing was 2.61 +/- 1.36 ng.dL-1 and the mean value of the patients without clubbing was 2.36 +/- 1.19 ng.dL-1. There was no significant difference between the values of the two groups. Although it is claimed that ectopic growth hormone is secreted in patients with lung cancer and is the possible mechanism for clubbing, this study did not show any relationship between clubbing and growth hormone levels.