The hue uniformity of the CIELAB system is investigated using a hue circle of Munsell colors at value 6 and chroma 14 and experimentally determined hue coefficient data. CIELAB hue differences for equal Munsell hue increments are found to vary yp to nearly a factor 4, and hue coefficients differ from the experimentally determined ones by! crp to 40% at certain wavelengths. Dominant wavelengths assigned by the CIELAB system to individual Munsell hues are found to vary YP to 35 nm from those of the Munsell Renotations. Four other color space systems nr-e compared with widely differing brit comparable results. The CIE 2 degrees color-matching functions are adapted to result in a set of opponent-color functions accurately representing the Munsell Hue and Chroma data. A call is made for the experimental determination of the "standard hue observer" as a step toward" nit improved color space/colar-difference formula.