Simulations for Al2O3 suggest that thermocapillary flow is the dominant mass transport mechanism for Czochralski growth in space vehicles. The residue of buoyant convection generated by microgravity is insignificant in comparison. Increasing the microgravity by tenfold, or switching it off completely, i.e., introducing "g-jitter," generates barely discernible changes in the flow field. On the other hand, neglecting thermocapillary flow leads to gross errors. These conclusions obtain even though the thermocapillary coefficient of Al2O3 is rather small compared with that of many other materials used in Czochralski growth. © 1980.