An instrument is described for the measurement of circular dichroism in the vacuum ultraviolet. A magnesium fluoride Rochon prism serves as polarizer and a stress plate modulator is the ¼‐wave retardation element. CD spectra have been recorded to 165 nm, but substitution of two elements in the optical system by available parts is expected to allow further extension of the wavelength region accessible. A previously used less successful system is also described which used a rotating Rochon prism and a Fresnel rhomb.