In this series of renal diseases, in addition to semiquantitative scoring of direct immunofluorescein images, the immune deposits were quantified by image analysis. The aim of this study was to evaluate quantitative measurements for diagnosis and prognosis of renal immune complex diseases. Immunoglobulin A (IgA) nephropathy (n=27, 54%), membranous nephropathy (n=8, 16%), membranoproliferative glomerulonephritis (n=8, 16%), and systemic lupus erithematosus nephritis cases (n=7, 14%) were evaluated by semiquantitative scores (SS) for IgG, IgA, IgM, C3, C1q, λ, and κ. The quantitative measures, intensity, mean and total optical density (MOD and TOD) were determined by image analysis software. There was positive correlation between SS; and intensity as well as TOD for 199 positive stained images, but not between SS and MOD. TOD was important for determining SS by linear regression. When all of the cases were considered, creatinin at the time of biopsy was only slightly correlated with intensity and TOD of IgM. Intensity and TOD, but not SS of IgA was significantly increased in IgA nephropathy cases with adverse histopathologic prognostic features. In 4 cases (8%) only TOD allowed identification of the predominantly deposited antibody. TOD and intensity seems to have better correlation with prognostic histopathologic features than SS. TOD may be useful for determining predominant immune deposit, a feature important for diagnosis.