The presence of visible gas on radiographs is associated with various pathological conditions, ranging from severe infections caused by gas-producing organisms to cutaneous and subcutaneous tissue disruption that allows an interface with the air. A high index of suspicion surrounds the finding of gas on radiographs because of the virulence of conditions such as gas gangrene and necrotizing fasciitis. We report a case in which proximal spread of gas in the soft tissues was not due to a spreading infection but rather to a cutaneous ulcer that, during walking activity, possibly acted as a one-way valve, allowing air to dissect proximally. To our knowledge, this mechanism of gas spreading in the soft tissues has not been reported previously. Our patient was informed that information concerning the case would be submitted for publication. Afifty-nine-year-old man with type-1 diabetes mellitus presented to our clinic for the treatment of a forefoot ulcer, under the area of the great toe, that had been present for more than five months. There was a history of a continuing serous discharge and increasing erythema during the week prior to presentation. Physical examination demonstrated swelling with erythema on the dorsum of the forefoot. The ulcer, located under the area of the first metatarsophalangeal joint (Fig. 1), was approximately 4 × 2 cm in size and exhibited no malodor or frank pus. Testing with a 5.07-g monofilament revealed a lack of protective sensation distal to the level of the ankle, but the patient had a palpable dorsalis pedis pulse and good capillary refill …