The AC losses of Bi-2212 multifilamentary round wires and the Rutherford-type cables were measured in transverse AC magnetic fields at liquid helium temperature by means of a standard pickup-coil method. The AC losses obtained for the strands were scarcely dependent upon the frequency of the external field in the range from 0.02 Hz to 10 Hz. This suggested that the hysteresis loss in a tightly coupled filament bundle be dominant. A remarkable improvement in the AC loss characteristic by reducing an effective diameter of the filament bundle are observed, while twisting the filaments itself does not contribute to the reduction in the AC loss. It was also found from the comparison between the AC losses in the strands and the cables that the AC losses in the cables mainly came from the individual strands.