Continuous cell lines (NIAS-Mb-19, NIAS-Mb-25 and NIAS-Mb-32) were established from the ovaries of pharate adults of the cabbage armyworm, Mamestra brassicae. One-and-a-half year elapsed before the cells multiplied steadily. The continuous cell lines consisted of a heterogeneous cell population, consisting of glass-attached flat cells and spherical free cells. The former varied considerably in shape and size. Most of the cells had finely branched cytoplasmic processes. Morphologically these three lines were not distinguishable from each other. In all the cell lines, diploid cells were predominant. The adhesiveness of cells to glass differed somewhat among the different lines. The patterns of amino acid utilization of these cell lines were characterized by marked consumption of aspartic acid, cystine, glutamine, histidine, isoleucine, leucine, methionine, tryptophan, tyrosine and valine, and by production of α-alanine and proline. These cell lines were susceptible to Chilo iridescent virus, and the infected cultures maintained a carrier state for many passages. The cell lines could be preserved for a long period by freezing or for a short period by placing them in a refrigerator.