Proteolytic enzymes can be extremely useful for the identification of clinically significant antibodies in blood grouping; however, they can also be destructive to certain agglutination reactions. ABO antibodies are the most clinically significant. A review of the literature reveals little research involving proteolytic enzymes and IgM antibodies. This study investigates the effects of various concentrations of the proteolytic enzyme bromelain on the agglutination of reagent A1 and B cells with donor plasma during ABO reverse grouping on the Olympus PK 7300 automated serology analyser. The optimum bromelain concentration improved or enhanced antigen-antibody reactions, causing a reduction in ABO failures. The results were analysed using an ANOVA test. An anomalous result was obtained at 0% bromelain where less ABO failures were generated than expected. Although most results were not statistically significant, the optimum bromelain concentration for ABO reverse grouping indicated was 0.25%. This work also highlighted the fact that ABO failures can be attributed to other factors such as sensitivity of reagent cells and antibody avidity. This study identified limitations and problems with the methods used and presents recommendations for future research which may assist in the clarification of the role of proteolytic enzymes in ABO reverse grouping.