Although techniques developed for forensic serology are designed for limited quantity stains and posses good sensitivity, they are often inadequate for the smeared, washed out, or diluted bloodstains submitted for laboratory analysis. In addition, current methods for characterizing seminal fluid stains are often limited in effectiveness because of a lack of material to analyze. In this study, seminal fluid stains and washed bloodstains were extracted and concentrated using a vacuum diffusion technique. The seminal fluid stains were typed in the PGM1 and Glo I systems before extraction and after concentration. The washed bloodstains were analyzed using the Hemochromogen test and the Anti-Human Globulin test before extraction and after concentration. Results showed that the method extended the degree of sensitivity for human blood or substance detection. When the bloodstain was allowed to set at least overniht before washing, the chances of detection were incerased. The concentration of bloodstains via vacuum diffusion can be applied to casework situations where a positive presumptive result is obtained and suspicion exists that the exhibit may have been laundered in some way. In addition, Glo I typing and concentration of seminal fluid stains by vacuum diffusion shows much promise and should be evaluated as to its practicality for implementation into casework situations. Photographs, data tables, and five-item references list are included.