The systolic blood pressures of rats that underwent parathyroidectomies and uninephrectomies reached hypertensive levels after implantation of deoxycorticosterone (DOC) pellets and were compared to those in rats with intact parathyroids bearing 20-mg or 50-mg pellets of DOC. Parathyroidectomy, however, ameliorated the incidence and severity of cardiac and renal lesions induced by DOC. The beneficial effect of parathyroidectomy on vascular lesions may well be attributable at least in part to a reduced level of calcium in the serum or to the absence of parathyroid hormone, which is involved directly in the regulation of calcium transport and influx into the cell. Parathyroidectomy significantly reduced the compensatory renal hypertrophy and splenomegaly induced by DOC, although cardiac hypertrophy and hepatomegaly induced by DOC were not affected by parathyroidectomy.