To evaluate the usefulness of International Classification of Diseases external cause-of-injury and poisoning codes (E codes) for public health surveillance of nonfatal injuries, we analyzed E codes from Indian Health Service (IHS) hospital records. E codes for unknown or unspecified causes were used for 25 percent of records. At two hospitals, 63 percent of E codes assigned by independent coders agreed; another 18 percent matched on general cause-of-injury groups. With uniform guidelines and increased training, E coding could provide a valuable, cost-effective method of quantifying and characterizing severe, nonfatal injuries.