The author incriminates two essential factors in renal lithogenesis: tubular and papillary. The tubular factor. Calcium microliths with a diameter greater than that of the collecting duct damage the wall of the duct, pass into the interstitium of the Malpighian pyramid and accumulate beneath the epithelium of the pitted zone forming the sub-epithelial plaque of Randall. Identification of such lesions is essential in avoiding the recurrence of lithiasis. However, in order for microliths to form, it is also necessary for there to be prolonged stagnation of urine in the collecting duct. Accumulation of such microliths forms the nucleus of the future calyceal calculus. The papillary factor. A whole series of papillary factors (entirely independent of the Randall plaque, the origin of which is tubular) favor the deposit of calcium on pathological papillary tissue. Thus, in the opinion of the author, combined tubular and papillary factors represent the essential factors in lithogenesis and, if they are not eliminated at the time of the treatment of lithiasis, are the essential factors in its recurrence.