The data recorded on several write-once (WO) and read-only-memory (ROM) compact discs has been examined byte by byte to determine the locations of all erroneous bytes along the spiral data tracks. This information has been used to determine error-burst and good-data-gap distributions, which specify the occurrence probability versus the length of an error event (burst) and the intervening segments of good data (gaps). The means for determining whether a given error event is a hard or a soft error event have also been developed. The burst and gap distributions exhibit generally similar characteristics for WO and ROM compact discs that are clean, although clustering of errors on the WO media is evident.