Responder lymphocytes were cultured with an equal number of irradiated stimulator lymphocytes from another donor for 6 days in RPMI 1640 (a modified Mc Coh's 5 A Medium). After 48 h incubation with PMA (phorbol 12-myristate), PHA (phytohaematogglutin) and 120 h with MLR (mixed lymphocytes reaction), the cells were labelled with 'โฌIH-thymidine. Cells were harvested in a scintillation counter. Globularia alypurn L. extracts were dissolved in HPLC quality ethanol or water and diluted in RPMI to concentrations ranging from 0.15610 pg/ mL. Extract solutions were added immediately after cell stimulation in the cell walls. Cyclosporin A was used as a control. Both the water and ethanol extracts of Globukuia ulypum L. demonstrated a dose response effect in all three systems of MLR, PHA and PMA with no statistical dflerence in water or ethanol extracts. The ICs were: PHA 1.14 pg/mL, PMA 1.05 pg/mL and MLR 2.06 pg/mL. The PHA and MLR IC, are approximately double the ICd for cyclosporin A (0.5 pg/mL). The effects of Glubuhria aljpum L. in PMA stimulated lymphocytes suggests it may suppress T cell function through a pathway that cyclosporin A does not effect.