There are no officially recognized regulations for the design and toxicity testing of adjuvants or adjuvant formulations; the former are also referred to as immunomodulators and immunopotentiators. At the “Immunological Adjuvants and Vaccines” meeting held in Greece in 1988, however, immunoadjuvant researchers discussed experimental toxicological tests that might be used to monitor new immunomodulators (1 ). The usefulness of these tests for the range of immunomodulators and adjuvant formulations was examined over a 2-yr period and subsequently, at the next NATO meeting in 1990, further recommendations were made (2 ). Although as yet, no final agreement has been reached and a variety of tests are still in use.