Extracts from seeds of Lotus tetragon., Cytisus sessil, and Laburnum alp. give lower titration scores with O H + ii cells than with O H + I + cells although both have a similar H status in studies with Ulex europ. reagent. Absorption and elution studies indicate that the Lotus extract contained anti-HI agglutinins with little activity for OH+ii cells whereas the Cytisus and Laburnum extracts contained anti-HI-H agglutinins that cross-reacted with O H+ ii cells. Lactose (7.1g/100ml) strongly inhibited the anti-HI-H reactions with little effect on the Ulex anti-H reagent. The anti-HI/HI-H reagents gave maximum activity at lower temperatures whereas the Ulex anti-H extract was just as active at 37°C as at 4°C.