Background: Paederus dermatitis, an acute erythemato-vesiculo-bullous dermatitis contracted through contact with the secretions of the Paederus species, is frequently seen among the people living in the south-west part of our country during spring and early summer months. Objective: This study was conducted to elucidate the responsible arthropod in Khuzestan province and to study the clinical spectrum as well as the pathological findings at different stages of the disease. Patients and Methods: Within a period of about 3 months, from April to July 1999, 72 patients referred to our clinic with erythema, vesicles, bullae, pustules, superficial skin necrosis or combination of few or all of these findings clinically suggestive of Paederus dermatitis. Biopsy samples were obtained from 19 patients at different stages of the disease stained by HE and studied histologically. All arthropods submitted by the patients and their families were crushed on our skin to identify the causative species. Results: The dermatosis is contracted through contact with the secretions of a Coleoptera species called Paederus Ramtinus. The painless and non-pruritic reaction developed 2-3 days following contact as erythema and vesiculation, which may gradually extend to necrosis and bullae. The pathologic changes were also variable and ranged from epidermal spongiosis to complete epidermal and upper dermal necrosis. Conclusion: Paederus dermatosis developed as a result of contact with the secretions of the species Paederus Ramtinus if by any way crushed or brushed off over the skin. The dermatosis is benign in contrast to its acute course no sequela is seen except for post inflammatory hyperpigmentation.