A numerical study was made of transient oscillatory flow modes in Czochralski convection. The temperature oscillation was computed over a broad range of the mixed convection parameters, 0.132 less than or equal to Ra/Pr Re-2 less than or equal to 1.303. This encompasses the buoyancy- and forced-dominant convection regimes. The computed period of oscillation was shown to be in excellent agreement with the relevant experimental results. Parametric studies were performed, which led to an understanding of the transition mechanism. Computational results were presented to disclose oscillating flow patterns and thermal fields. The influences of melt level and of the size of crystal rod on the onset of oscillation were examined. The effect of crucible rotation (Re-c) was also evaluated. The oscillatory flow modes were analyzed in derail for a realistic,low value of Pr.