A search for possible lithogenous factors was under-taken in a group of 42 lichen planus (LP) patients (15 with urolithiasis and 27 without). Normal mean values of calcium, phosphorus, uric acid and creatinine were found in the serum and in the 24-hour urine collection. However, 9 patients (21%) manifested laboratory deviations consisting of hyperuricemia, hyperuricosuria or hypercalciuria, or combinations of the three. The prevalence of hyperuricemia among LP patients was greater than in matched controls and vis-à-vis the recorded prevalence of hyperuricemia in the general population and in other calcium stone formers. These findings may suggest involvement of metabolic defects in LP.