High-voltage electric burns are often associated with deep muscle damage in addition to a limited cutaneous burn. Technetium-99m stannous pyrophosphate (99mTc-PYP) scintigrams were evaluated as a diagnostic tool to detect and localize both large and focal areas of skeletal muscle necrosis. Scintigrams were performed in 14 patients between the first and fifth postinjury days and imaging was done over areas of suspected and clinically apparent muscle injury. Muscle damage was identified by an increased cellular uptake of the tagged material. All 14 patients had gross and histologic evidence of muscle necrosis. Muscle necrosis was identified as early as 24 hours and as late as 6 days postinjury. The location and extent of muscle injury was correctly ascertained preoperatively in all patients.