In 80 adult kidney stone formers (52 with reversible and 28 with irreversible renal impairment) laboratory and clinical data were evaluated to estimate the share of abnormalities in the metabolism of stone forming substances in the development of renal impairment, and to search for the causes of the irreversibility of renal impairment. The study confirmed the previous results from this laboratory suggesting a causal relationship between renal impairment and metabolic disorders. No significant differences in the incidence of metabolic disorders or in therapy have been found in patients with irreversible renal impairment as compared to those with progressive deterioration of renal function. Irreversible renal impairment developed in relationship with bilateral kidney stone formation and recurrent urinary infection.