Lectin-like proteins from seven medicinal plant species of South Africa possessing well-documented antibacterial effects were examined for the interaction with two Gram-positive bacterial pathogens Staphylococcus aureus and Bacillus subtilis. Agglutinins elicited selective aggregation reactions with bacterial strains. Hypoxis hemerocallidea and Combretum mkhuzense agglutinins aggregated S. aureus at 4 and 5 microg ml(-1) of protein concentrations, respectively. B. subtilis was aggregated by C. mkhuzense, Kniphofia spp. and Tulbaghia violacea agglutinins at relatively high concentrations. The inhibition of bacterial growth at the initial stages of multiplication was observed in the presence of particular plant agglutinins. Suggestions are given about possible employment of agglutinins from medicinal plants in clinical microbiology. The possible contribution of lectin-like proteins to pharmacological effects associated with microbial infections is presumed.