Abstract: Ambient temperatures in tropical countries across the equatorial belt are adversely high. Thus, the operating temperatures of electrical machines in these countries are uncomfortably high even when, the machines operate at rated load. Nigeria as a tropical and developing country has had to contend with this unfavorable thermal condition for electrical machines. Most of the drive motors in Nigeria are imported and many of them come with class B insulation. In this study, eight sample varieties of Nigerian wood species-Mahogany, Obeche, Iroko, Afara, Danta, Opepe, Abeza and Aper and the two most commonly imported class B insulating materials-fiber glass and leatheroid are experimented with to compare their ability to maintain insulation integrity at higher temperatures. Impregnated samples of the eight wood species and samples of leatheroid and fiber glass were subjected to a heat-run in a sealed industrial oven. The insulation resistance of each sample was measured at regular temperature intervals, until the sample burns out. Tables show the values of weight, insulation resistance and temperature. The results show that at the class B limiting temperature of 130°C, leatheroid had an insulation resistance of 6 MΩ, while that of fiber glass was 8 MΩ. The eight wood samples had insulation resistance above 30 MΩ. At the higher temperature of 150°C, the insulation resistances of leatheroid and fiber glass collapsed to 1 and 1.4 MΩ, respectively while that of the wood species was a minimum of 15 MΩ. At a much elevated temperature of 170°C, both leatheroid and fiber glass were burnt but, the insulation resistances of the eight wood species were up to 8 MΩ. Thus, the wood species exhibited higher insulation integrity at higher temperatures than leatheroid and fiber glass. These wood species through some careful chemical synthesis could be made more malleable and consequently, serve as alternative and cheaper machine insulating materials to the imported leatheroid and fiber glass.