Based on experience accumulated in a number of laboratories, a standar
dized protocol for phototoxicity testing in experimental animals by th
e dermal route is presented. By conducting a limited interlaboratory s
tudy, demonstrating a high degree of consistency using 8-methoxypsoral
en (8-MOP) and acridine, the sensitivity and reproducibility of the pr
oposed methodology is demonstrated. Important aspects of performing ph
ototoxicity testing are discussed.