An indirect immunoalkaline phosphatase (IAP) technique was used to evaluate the glomerular deposition of immunoglobulins, C3, C1q and fibrinogen. In 80 renal biopsy specimens the results obtained using this technique were compared with those obtained by direct immunofluorescence to see if it could be used as a viable alternative. The IAP technique was straightforward to perform, it yielded quick results, and was highly reproducible, provided that a standardised short fixation period of two and a half hours was used. For the detection of immunoglobulin deposits, the IAP results correlated well with those of immunofluorescence. Despite poorer performance in identifying complement components and fibrinogen it could, within certain limits, provide an adequate diagnostic alternative to immunofluorescence. Each technique gave false negative results, those of immunofluorescence being related to its failure to identify mesangial deposition of IgA in two cases where its distribution seemed to be focal, and those of IAP to a failure to detect linear deposition of IgG in all three cases of anti-glomerular basement membrane disease.