Antineoplastons are naturally-occurring peptides and amino acid derivatives which control neoplastic growth. The theory of antineoplastons was conceived through the application of the cybernetic theory of autonomous systems to studies of peptides in human blood. The original research began in 1967, when it was noticed that there were significant differences in the peptide content in the serum of cancer patients as compared with the control group. Since similar peptide fractions were isolated from urine, a research programme was established for the identification of antineoplastic peptides from urine. Medicinal use of urine and urine extracts has been known for centuries in ancient Egypt, Greece, Rome, India and North and Central America. In modern times, the first study of growth-inhibiting substances in urine was conducted in 1937. The research on urinary peptides has a long history and was initiated by a Polish researcher, S. Bondzynski, in 1897. Antineoplastons were found to be completely different from peptides and amino acid derivatives isolated from urine by other authors. Research on antineoplastons led to the isolation of different peptide fractions from urine, named Antineoplaston A1, A2, A3, A4 and A5, which possessed high anticancer activity and low toxicity. The first active component was identified as 3-phenylacetylamino-2,6-piperidinedione and was named Antineoplaston A10. Two synthetic derivatives of Antineoplaston A10 were named Antineoplaston AS2-1 and AS2-5. All antineoplaston formulations were submitted for Phase I clinical studies in advanced cancer patients. The treatment was free from significant side-effects and resulted in objective response in a number of advanced cancer cases.(ABSTRACT TRUNCATED AT 250 WORDS)