In this study, the temperature-dependent behavior of the retention of C, H, O, S, and N in solid fuel chars under pyrolysis conditions is explored as the primary interest. A fuel's organic element retention during pyrolysis is fundamentally important since the subsequent oxidation mechanisms of the two distinct product fractions of pyrolysis, char and volatiles, are different in nature. The chemistry of chars prepared at 275-1100 degrees C from nine solid fuels (three woody, four herbaceous, two fossil) in a lab-scale furnace is compared to that of their respective precursors. Two measures, "retention" and "relative retention", are used to quantify each element's tendency for partitioning between char and volatile matter. The results show that release of C, H, and O as the temperature increases is similar for all the biomass fuels. Carbon retention, as expected, mimics the behavior of the char yield for both fuel classes, resulting in an increasing enrichment of C in the char as temperature increases. Simultaneously, a steady preferential loss of H and O occurs, such that at 1100 'C, H and O are essentially fully depleted. Unlike these three organic elements, the release behavior during pyrolysis of the remaining two elements, S and N, can be strikingly different even within the biomass fuel subclasses. Biomass chars initially lose more than 50% fuel-S, likely organic S, followed by very little additional S release as temperatures rise above 500 degrees C. Sulfur recapture, which has been discussed in the coal literature, is seen here for a South African coal char between 500 and 750 degrees C. Generally speaking, the coals hold about half or more of the original fuel-S in their chars up to 1100 degrees C. The two coals steadily release N from their chars beginning at similar to 400 degrees C and continuing through 1100 degrees C, at which temperature slightly more than half of coal-N remained in both cases. For biomass fuels, the behavior of N during pyrolysis appeared somewhat similar up to 750 degrees C; however, above this temperature, N retention in the char is highly variant and somewhat peculiar. All seven biomass types released at least half of the fuel-N to the volatiles by 400 degrees C. Gradual N release then persists up to 750 degrees C. However, chars from three biomass types continued gradual N release, while the other four tended to reclaim N into the char between 900 and 1100 degrees C. Exploring this phenomenon, additional experiments were made in which the sample size, heating rate, purge gas, and contact arrangement of the purge gas were altered. Results of these secondary experiments suggest that, in addition to some volatile-N recapture, nitrogen from the purge gas is taken up by the chars at these temperatures. Importantly, the uptake is relatively large compared to high-temperature volatile-N release for fuels with low nitrogen content. The undesirable fate of the incorporated N during the subsequent combustion of such chars, i.e., the propensity for forming NO, appears greater for char-N that is introduced by N-2 purge gas than by recapture of previously devolatilized N.