Although numerous methods for regenerating articular cartilage have been investigated, the regenerated tissue showed various histological findings from hyaline-like cartilage to fibrous tissue. Without biopsy, we are unable to know whether the cartilage regeneration method was histologically successful or not. We developed a new ultrasonic evaluation system for articular cartilage using the maximum magnitude (MM) from ultrasonic analysis. The purpose of this study was to investigate the usefulness of ultrasonic judgment of the cartilage regeneration procedure. Using our system we quantitatively evaluated tissue-engineered cartilage in rabbit cartilage defects. The specimens were retrospectively divided into two groups on the basis of histological findings and investigated whether significant differences in ultrasonic analysis could be found between the two (group H: hyaline-like cartilage group, successful; group F: fibrous tissue group, failure). In the ultrasonic findings, the MM was 1.11+/-0.32 in group H and 0.65+/-0.18 in group F and these differences were significant (P=0.00061). Our results suggest that the ultrasonic evaluation system used in the present study is capable of judging the success or failure of cartilage regeneration procedures, and therefore, it could be a valuable tool arthroscopic diagnosis of cartilage regeneration.