Xylitol is a fermentation product of xylose that can be used as a sweetener by diabetics. Five novel Kluyveromyces marxianus yeast strains, IMB1, IMB2, IMB3, IMB4 and IMB5, have shown the ability to grow on xylose and produce xylitol. In comparison to chemical synthetic xylitol production, biological production can be more cost effective since no expensive metal catalysts and high temperatures are needed. The five K. marxianus IMB strains were tested at temperatures ranging from 25°C to 45°C with xylose as the sole carbon source. IMB2 was found to be the best xylitol producer among the IMB yeast. Product yields (YP/S) up to 0.90 g/g at 40°C with 1.0 g/l initial cell mass and 50 g/l initial xylose concentration were observed for IMB2.