The potential of n-Valeraldehyd to cause acute dermal irritation or corrosion was assessed by a single topical application of 0.5 ml of the test substance to the intact skin of 3 White New Zealand rabbits for 4 hours under semiocclusive dressing. The average score (24 to-72 hours) per animal was calculated to be 0.3, 3.0 and 2.0 for erythema and 0.0, 1.0 and 0.3 for edema. The skin findings were not reversible in 1 animal within 14 days after removal of the patches. Symptoms observed and described in the respective observation table in detail together with the average score for irritation indicate an irritant property of the test substance to the skin. Under the test conditions chosen and considering the described findings n-Valeraldehyd gives indication of an irritant property to the skin.