Abstract: A multicolor particle analyzer and method is described. The particles each of which either naturally fluoresce or are tagged to fluoresce at distinctive wavelengths are caused to flow through an analyzing volume where fluorescence is excited by an impinging light beam. A tunable optical filter repetitively and sequentially passes emitted light at each of the characteristic wavelengths as each particle travels through the analyzing volume and the light transmitted through the optical filter is received by single detector which provides output signals representative of each distinct wavelength of light emitted by the particle.