We recently treated two patients with engine block-muffler contact burns and greatly underestimated the devastating injuries to bone, deep fascia, and muscle. As a result, each patient required multiple procedures to close their burn wounds. Ten-year data from the University of Washington Burn Unit confirmed our observation that these burns tend to be considerably deeper than suspected. Eighteen patients with contact burns from engine parts were identified from 1980 through 1990. Nine (50%) of these were initially recognized to be fourth-degree and five (28%) were third-degree thermal injuries, showing that these are deep burns. Eight patients required fascial excisions and four required debridement of devascularized bone. The mean burn size was only 6% total body surface area; however, the patients with fourth-degree burns had an average graft take of only 56% and required a mean hospital stay of 44 days. Patients with third-degree burns also had suboptimal graft take and some required prolonged hospitalization. Thirty-six percent of patients required flaps either as the initial procedure or as a second procedure following an autograft. The four patients with partial-thickness burns healed without surgery and their average length of hospital stay was 3 days. Of the entire group, only four healed without surgery and only five healed with a single operation. Our 10-year data indicate that engine block contact burns are usually small, but most are deceptively deep, involving tendon, muscle, or bone. If the burn appears full thickness, suspicion must be very high at the initial surgical procedure that there is deep tissue destruction.(ABSTRACT TRUNCATED AT 250 WORDS)