Histologically, warts are benign lesions, with hypertrophy of all layers of the dermis (Fig. 1a), resulting in acanthosis (thickening), papillomatisis (folding) and hyperkeratosis (increase in the horny layer) often with abnormal keratohyaline granules. Vacuolation of cells occurs in the upper layers and inclusion bodies are sometimes observed. Different types of cutaneous warts can show characteristic changes and for the interested reader, the histological illustrations in Croissant et al. (1985) remain useful. Resolution using the electron microscope reveals densely packed virus particles in crystalline array in the upper stratum granulosum and stratum corneum (Fig. 1b). Warts usually disappear spontaneously but occasionally may be resistant to treatment. Regrowth of lesions after treatment is frequently due to persistence of the virus in the skin surrounding the original wart.