Recent progress in biotechnology, including recombinant DNA (rDNA) technology and cell culture technology, has enabled us to produce new medically useful agents intended for human use. These agents include therapeutic peptides and proteins derived from rDNA-modified cell substrates, continuous cell lines, diploid cell lines, and hybridoma cell lines, gene therapy products, cellular therapy products, and therapeutic protein products and cellular products derived from transgenic animals. To enable these products to be of use in human therapy, it is essential that suitable measures be taken by manufacturers and regulatory authorities to assure their quality, efficacy, and safety. This article describes points based on the latest sound scientific principles to be considered when producing, testing, evaluating and controlling biotechnological products for human therapy, especially with respect to their characteristics, quality and safety.