The histories of 121 Stage II melanoma patients were reviewed to determine the value of monitoring serum LDH in postoperative follow-up examinations. Charts of 58 Stage III patients who had autopsies at UCLA also were reviewed to define the relationship between an elevated LDH and liver metastases. The sensitivity and specificity of LDH as an indicator of disease recurrence were 72.1% and 97.0%, respectively. As an indicator of liver metastases, LDH had a sensitivity and specificity of 95.1% and 82.8% in the Stage II patient group and 86.5% and 57.1% in the Stage III autopsied group. An elevated LDH was the first indication of recurrent disease in 11/88 (12.5%) Stage II patients and was almost as frequent an indicator of recurrent disease as pulmonary metastases found on chest x-ray. Mean survival following elevation of LDH was 5.9 months whether or not liver metastases were present. Monitoring of serum LDH can provide useful information in the postoperative follow-up of patients with melanoma.