In this study we investigated the relationships between the thermal properties versus maturity and fineness (H) of 80 selected cotton fiber samples. The instrument measurements for maturity and H were (1) micronaire as determined with a high-volume instrument, (2) maturity ratio and H as determined with an advanced fiber information system, and (3) gravimetric H as determined by the cut-and-weigh method. Three regions of thermal decomposition were observed between 37 and 150 degrees C for region 1, between 225 and 425 degrees C for region 11, and between 425 and 600 degrees C for region III. Complete decomposition of the fiber occurred at 600 degrees C. The results showed significant effects of the H/maturity indicators on the weight loss and the peak temperatures in regions II and III. High micronaires (coarse or very mature fibers), high maturity ratios, and low standard H values were associated with low weight losses. However, high weight losses were associated with high primary cell wall areas per unit mass. (c) 2006 Wiley Periodicals, Inc.