Method for determination of percentage T cell content of lymphocyte

A fully automatic method for determining the percentage T-cell content of lymphocytes which have been sampled wherein said lymphocytes comprise T-cells, B-cells and Null-cells, said method comprising scanning a test specimen with a pick up device to produce image signals, discriminating a lymphocyte from other cells contained in said specimen from the output level and regional information of the image signals, searching the data marginal to those of the cells discriminated as a lymphocyte to detect pixels corresponding to the image signal output level different from that corresponding to the lymphocytes or background, discriminating a T-cell from other lymphocytes from the number of detected pixels, and determining and displaying the percentage T-cell content of said lymphocytes.