To assess the distribution pattern of Langerhans cells (LC) in normal porcine skin, epidermal sheets from six anatomical sites from three age-matched groups of male and female pigs were stained for ATPase activity. This histoenzymological technique is considered specific for Langerhans cells in normal epidermis. No statistically significant differences were observed between mean Langerhans cell density per mm2 of epidermis from male and female pigs, nor between different anatomical sites in the same age group. Statistically significant differences (P less than 0.0005) were observed when comparing group A one- to two-week-old piglets (463 to 518 LC mm-2) with group B six month olds (641 to 804 LC mm-2) and group C two years and over sows (741 to 830 LC mm-2). Morphological variations in the skin of young piglets, much thinner and with rudimentary or no epidermal rete pegs, could account for this significant variation.