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Diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy was used to compare changes in organic chemistry of 10 species of foliar litter undergoing in situ decomposition for 1 to 12 years at four forested sites representing a range of climates in Canada. Three types of foliar litter (conifer, black spruce; deciduous, trembling aspen; and a grass, fescue) were studied on all four sites plus seven additional types (Douglas, fir; western red cedar; white birch; jack pine; beech; bracken fern; and tamarack) studied at the warmest site (Morgan Arboretum [MAR]). For all litter samples, DRIFT spectra were collected, and carbon and N were contents determined. A subset of samples (10 types x 5 years for MAR, three types x 5 years for the other sites) was analyzed by classical chemical methods for proximate fractions. Spectra for subsets of chemically analyzed samples from MAR were used to prepare partial least squares calibration equations for each chemical variable. These calibrations were then used to predict chemical concentrations for samples in a reserved subset, in intervening years, and from the three other sites, and then validated against measured values. Results indicated a trend of decline in proportion of nonpolar and water-soluble extractables with an increase in proportion of acid unhydrolyzable residue. The DRIFT was demonstrated as a fast and simple analysis method for analyzing large numbers of samples to give good estimates of litter chemistry. A single nondestructive sampling using as little as 0.1 g of sample gave reasonable values of carbon, N, and proximate fractions.