The use of synthetic peptides to delineate epitopes recognized by major histocompatability complex-restricted cytotoxic T lymphocytes has been well documented. In the present study, we report a method for the generation and assay of peptide-specific cytotoxic T lymphocytes adapted for the field situation where quantities of blood are often limited. From a single bleed of the donor and using minimal quantities of peptide (less than 5 micrograms/ml), up to 100 potential epitopes could be screened within a short time frame. Subsequent cloning of positive cultures for further analysis of defined epitopes is permissible. The system is readily adaptable to a wide range of viral, parasitic or bacterial infections.