This paper describes a new automated method for objectively counting and sizing neps in cotton fiber. The instrument opens and individualizes the fibers and neps in a 500 mg sample which then pass through an electro-optical sensor. The output from the sensor is analyzed by a microprocessor for the nep count and size. Four specimens per sample were required to get reproducible results. About 15 minutes is required to test a sample. Comparisons with card web nep counts were made. Data on daily level checks are given. Nep counts increased when gin lint cleaners were used and neps in in-process stock from textile processing were analyzed.