AbstractPhthalimide fungicides (captafol, captan and folpet) enhanced the accumulation of fenarimol by the mycelium of a wild‐type strain and a fenarimol‐resistant strain ofAspergillus nidulans. The accumulation is ascribed to inhibition of active efflux of fenarimol from the mycelium. It is assumed that the synergistic action observed between the phthalimide fungicides and fenarimol with respect to fungitoxicity, was caused by the increased accumulation of fenari