Crystallization of hen egg-white lysozyme and horse-spleen ferritin wa
s carried out under a steady and uniform magnetic field of 10 T and co
mpared with the crystals grown under 0 T. It is clearly demonstrated t
hat a magnetic field reduced the number of nuclei and not only oriente
d the crystals but also modified the habit of protein crystals. The pr
esent experimental result indicates that application of a magnetic fie
ld is an efficient method for growing a small number of large crystals
.