Filter paper (FP), acidic wood-free paper (AP), neutral wood-free paper (WP) and neutral wood-free paper containing recycled fibers (RP) were heated to investigate the permanence of the neutral wood-free papers. The folding endurance of AP become zero after being heated for 10 days, while RP and WP heated for 28 days lost their folding endurances by 59.7% and 53.6%, respectively. This indicated that although the deterioratrion of the neutral wood-free papers was not so fast as that of the acidic wood-free paper was, it was progressing during accelerated aging. The Raman spectra of RP and WP suggested that thermohydrolytic degradation of cellulose, hemicellulose and starch in the papers took place during heating. The analyses on RP and WP by pyrolysis-gas chromatography suggested that the losses in the folding endurances of the papers depended deeply on the contents of rosin sizes and polyacrylamides in the papers. Printing with a laser printer or a copier greatly reduced the folding endurances of the papers. FP, AP, RP and WP heated for 28 days lost their brightnesses by 6.2%, 17.2%, 11.6% and 10.3%, respectively. The neutral papers also suffered significant losses in the brightnesses during the accelerated aging. The fact that RP lost 13% more brightness demonstrated that recycled fibers and papermaking additives in the papers influenced the brightness stability of the papers.