Vitrinite reflectance on dispersed sedimentary organic matter is traditionally determined from histograms of vitrinite and inertinite reflectance measured on either whole rock samples or kerogen concentrates, or from particles usually in whole rock preparations chosen by morphology and relative reflectance to be first-cycle vitrinite. This paper discusses an alternative method: discrimination of first-cycle vitrinite using apparent maximum and minimum reflectance data plotted on reflectance crossplots. The use of crossplots increases the confidence that the macerals identified as first-cycle vitrinite are optically similar. The maximum-minimum data, in this study, were collected on a quantitative reflectance microscope outfitted with rotational polarization, a technique that eliminates the usual difficulty in collecting such data on very small macerals by stage rotation. (C) 2000 Elsevier Science B.V. All rights reserved.