A cell line designated "HIBSPP" was established from a human malignant choroids plexus papilloma of 29-year-old Japanese woman. This line grew well without interruption for 3 years and was subcultivated over 70 times. The cells were spindle, oval, and polygonal in shape, and neoplastic and pleomorphic features, a jigsaw puzzle-like arrangement, multilayering and forming papillary structures without contact inhibition. The cells proliferated slowly, and the population doubling time was about 69 hours. The chromosome number showed a wide distribution of aneuploidy. The mode was in the hypotetraploid range, and many marker chromosomes were observed. The culture cells were easily transplanted into the subcutis of nude mice and produced the tumor resembling the original tumor.