The tris (hydroxymethyl)aminomethane salt of d-10-camphorsulfonic acid (TRIS-CSA) provides a convenient, non-hygroscopic alternative to the parent compound in the calibration of circular dichrometers. The molecular ellipticities, [6], of TRIS-CSA at 291 and 191 nm are 8015± 11 and -16, 130± 40 deg cm2dmol−1, respectively. The circular dichroism (CD) maxima in terms of δϵ are 2.429 1 cm−1mol−1at 291 nm and -4.888 1 cm−1mol−1at 191 nm. TRIS-CSA has an ORD peak at 306.5 nm, a zero crossover at 292 nm, and a trough at 270.5 nm (molecular rotation, [M]306.5=4475± 10, [M]270.5= -5615± 10 deg cm2dmol−1), and a molar absorptivity, ϵ, of 35.9± 0.2 1 cm−1mol−1at 286 nm.