Of 20 cases of rupture of tendo calcaneus following sports activity, 19 were complete and required surgi-cal repair, tbe other being incomplete, was treated with a cast with the foot in plantar flexion for 6 wk. Recovery was seen in all within half a year. Rupture in the mid-portion constituted 85%. Microangiog-raphy of amputation specimens and cadaveric tendons and histological study of cadaveric tendons showed thatblood supply was poorest in the mid-portion. Electronmicroscopy revealed hyaline degeneration in the tendon,which might account for the rupture. Mo-target X-ray was helpful in the early diagnosis of rupture and tendinitis calcaneus in 88 patients(170 films ). Early sutgical repair is preferred if indicated. Overloading should be avoided to prevent rup-ture. A 500-m. jogging daily helps the sufferers of tendinitis with better circulation. Local application ofsteroids should be administered with caution.