Large volcanic eruptions provide a test of the ability of climate models to reproduce vertical patterns of temperature response on time scales of 1-3 years. We compare the vertical profile of volcanic signals in the AR4 twentieth century coupled GCM runs with radiosonde observations for the past three major eruptions. After accounting for the ENSO signal, all models show warming in the stratosphere and cooling in the troposphere and surface, with tropospheric amplification of surface cooling in the tropics. Observed volcanic effects are sensitive to treatment of the ENSO and QBO signals. Preliminary results show that volcanic cooling for Pinatubo in the tropical troposphere is less in many models than in the observations. Larger differences occur in the stratosphere. We examine the effect of the differences on vertical trend profiles.