Localization of adhesive glycoproteins as the extracellular matrix and their cell surface receptors (integrins) were studied in an attempt to clarify their roles in the progression and aggravation of IgA nephropathy. The relationship between their localization and factors associated with clinical progression was then investigated in 65 patients with IgA nephropathy. The indirect immunoperoxidase method was used to study the distribution of fibronectin (FN), vitronectin (VN), fibronectin receptor (FNR) and vitronectin receptor (VNR). In all cases, FN was present in the glomeruli, mainly confined to the mesangial region, and in some cases, it was observed along the glomerular capillary loops. An expanded mesangial region accompanied higher FN distribution. FNR was present in the mesangial region and glomerular capillary loops, and was higher in the expanded mesangial region. VN was positive in 51 of 65 cases. In all cases, VNR was present in the mesangium and glomerular capillary loops, and its distribution was more predominant in and along the capillary loops than in the mesangial region. The expanded mesangium accompanied higher VNR distribution. There was a significant correlation in distribution between all factors with the exception of VN and FNR. FN, FNR and VNR increased significantly as a degree of histological damage. However, VN was not significantly associated with the degree of histological damage in positive and negative groups. The distribution of FN, FNR and VNR was associated with clinical aggravation factors although the distribution of VN was not. In conclusion, the distribution and functional alteration of FN and integrins in the glomeruli appear to be involved in the progression and exacerbation of IgA nephropathy. However, VN has not yet been clarified.