The effects of repetitive low-voltage stimulation of deep cerebellar structures upon tonic stretch reflex discharges of triceps-surae alpha motoneurons were compared, in decerebrate cats, before and after interruption of the gamma-muscle spindle loop. The qualitative character of facilitory as well as inhibitory cerebellar alpha effects remained unchanged under the two conditions. Acute gamma loop interruption resulted in quantitative reductions of the control stretch reflex and of its cerebellar modulations. A compensatory increase of the muscle''s resting length, after removal of the gamma support, restored the original alpha cell reactions. Comparison of the frequency-extension diagrams of single alpha units, obtained under the different experimental conditions by stepwise increased muscle extension, indicated that in cerebellar facilitation synergistic influences via gamma as well as alpha pathways were involved. Cerebellar inhibition reduced the alpha cell responsivity without significantly suppressing their gamma support. The qualitative independence but quantiative dependence of the cerebellar alpha effects upon the amount of available gamma support are discussed with respect to their functional purpose.