Each of these procedures has been suggested for use in enhancing fingerprints made in blood or other substances containing protein. Seventeen substrates were used. Samples of each material were prepared by placing a bloody fingerprint on each sample, using whole human blood. One group of samples was exposed to vapor-phase cyanoacrylate (CA) for 15 minutes. The second group received no preprocessing. To evaluate the effectiveness of each staining procedure, samples from each group (CA and unexposed) were identically processed using one of the stains, and the results were compared. Study findings did not yield a general rule regarding the utility of CA preprocessing. On some surfaces, CA preprocessing may interfere with the visualization of latent impressions by the stain. Of the stains examined, Amido Black is generally the best choice for processing latent impressions in blood. CA preprocessing is not deleterious for most substrates which are to be subsequently processed with Amido Black. Crowle's stain can also be effectively used to process impressions in blood. CA preprocessing may sometimes be used prior to Crowle's stain; however, this is not advisable in all cases. Coomassie is the least effective of the three stains for visualizing latent impressions in blood. 6 figures, 4 references.