Enteric coated dexchlorpheniramine maleate (DCPA) tablets and pellets with varying coating thickness were subjected to several in vitro tests after irradiation by thermal neutrons in a flux of 1. 1 x 10(13) n cm-2 s-1 for 2, 4 or 15 min. The appearance of the tablet formulation changed extensively after exposure of the tablets to pile radiation. The irradiation caused the film to loosen from the surface of the core, indicating the generation of gases during the irradiation process. Already after irradiating the tablets for 2 min the disintegration and dissolution behaviour were significantly changed. The extent of tablet damage increased with increasing time of exposure and increasing thickness of the coating. Compared with the tablet formulation, the cores could resist a larger amount of irradiation since dissolution behaviour of the cores was only affected after 15 min of irradiation. This indicates that the irradiation procedure initially affects the coating of the formulation. Although the dissolution behaviour of the pellet formulations changed significantly after the irradiation procedure, the changes were too small to be attributed exclusively to radiation damage.