We sought to study the effect of synovectomy on the surface morphology of articular cartilages of the rabbitknee using scanning electron microscopy (SEM). Fifteen rabbits were surgically synovectomised and allowedto regenerate their synovia during time intervals ranging from 3 to 44 wk. Cartilage specimens were shavedfrom 5 distinct articular sectors of synovectomised, contralateral and sham-operated knees and prepared forSEM using tannic acid. Applying structural reinforcement by tannic acid was found to secure the in vivosurface morphology of the cartilages and thus production of surface irregularities during preparation wasexcluded. The surface morphology of cartilages both from the synovectomised and contralateral joints wasfound to differ from that of intact healthy rabbits. A ‘chaotic’ nature of the altered cartilaginousmorphology persisted as late as 44 wk postsynovectomy. Cartilages from sham-operated joints did not differ detectably from normal cartilages.