The filament count of a carbon fiber tow is increased by spreading and commingling the carbon filaments of a first tow with the carbon filaments of a second tow. The carbon filaments of the first and second tows are spread apart using a gas stream. The spread tows are aligned with each other and brought into contact as they pass over a grating in the presence of the same or a different gas stream to form an entangled tow. The entangled tow is then formed into a combined tow. The modulus and denier of the carbon filaments in the first and second tows may be the same or they can be varied to provide combined tows with a wide range of filament counts and filament combinations.