FIELD : medicine.SUBSTANCE : invention relates to medicine and is a method for determining an index of manifestation of interstitial renal fibrosis in myelomal nephropathy, involving light microscopic examination of kidney biopsy material stained by Masson with trichrome, method is characterized by that digital processing and computer morphometric analysis of the optical image of the cortical substance of the kidney biopsy material is carried out, wherein the cortical substance area of the kidney (sCS) is successively measured, as well as its constituent structures : area of all glomeruli, including sclerosed (sGlom), tubular lumen area (sTubL), area of cylinders, including pathological in lumen of tubules (sCyl), then calculating the area of interstitium (sI) by formula : sI=sCS-(sGlom+sTubL+sCyl) and calculating the area of fibrous pathological tissue in interstitium (sIF) throughout the cortical substance of the kidney biopsy material, and the interstitial fibrosis manifestation index (IIF) is calculated by formula : intensity IIF=sIF/sI*100.EFFECT : invention provides enlarging technical means for determining the manifestation of interstitial renal fibrosis in myelomal nephropathy with high accuracy.1 cl, 2 dwg, 3 tbl, 2 ex