Silver carp insulin crystallizes in space group P2_12_12_1 with cell dimensions a=96.73(8), b=57.74(7), and c=53.88(9). There are six molecules in an asymmetric unit. The orientations of non-crystallographic three- and two-fold axes have been worked out by the rotation function method and the results indicate that silver carp insulin has a spatial structure and a mode of aggregation similar to that of the rhombohedral 2-Zn pig insulin, though the crystal packings are different. In the present paper, we discuss the influence of the changes in sequence of insulin upon crystallization behaviour and packing of molecules Silver carp insulin crystallizes in space group P2_12_12_1 with cell dimensions a = 96.73 (8), b = 57.74 (7), and c = 53.88 (9). There are six molecules in an asymmetric unit. and two-fold axes have been worked out by the rotation function method and the results that silver carp insulin has a spatial structure and a mode of aggregation similar to that of the rhombohedral 2-Zn pig insulin, though the crystal packings are different. In the present paper, we discuss the influence of the changes in sequence of insulin upon crystallization behavior and packing of molecules