Antineoplaston A5 is a mixture of small peptides and amino acid derivatives isolated from human urine which show a unique pattern of growth inhibition in the tissue culture of human neoplastic cells and no significant animal toxicity. Clinical trials described in this paper involved 15 patients diagnosed with advanced neoplastic diseases. The patients' diagnoses included: lung cancer, stage III (4 cases); breast, stages III and IV (3); colorectal, stage IV (2); bladder (2); and single cases of adenocarcinoma of the jejunum, stage IV; adenocarcinoma of the prostate, stage IV; adenocarcinoma of the ovary, stage IV and astrocytoma, grade IV. Antineoplaston A5 was administered daily in divided doses intravenously through a subclavian vein catheter. The formulation was given from 47 to 130 days. The highest dosage attained was 153 mg/kg/24 h. Adverse effects included febrile reaction in five patients, arthralgia in one patient and premature beats and pressure in the chest in one patient. The side-effects were very mild and usually experienced only once during the entire course of treatment. Desirable side-effects included increase of platelet count, increase of white blood cell count and hypertrophy of epidermis. Nine patients (60%) had objective response to the treatment. They were diagnosed with cancer of the lung (3 patients), breast (2), colorectal (2) and bladder (2). Four patients had increasing disease and two patients were classified as having stable disease without objective improvement.