The thermoregulatory characteristics of three species ofCryptomys from Zambia and Angola are examined and, togetherwith published data on four other species of Cryptomys fromsouthern Africa, used to determine whether scaling occurs inthis genus of subterranean rodents. The thermoregulatoryproperties of acclimated giant Zambian mole-rats, Cryptomysmechowi (xBAR=267 g), Angolan mole-rats, Cryptomys bocagei(xBAR=94 g) and Zambian common mole-rats Cryptomys hottentotusamatus (xBAR=77 g) are,as follows. Mean resting metabolic rates(RMRs) within the respective thermoneutral zones were 0.60+/-0.08 cm3 O2 g-1 h-1 (n=12) for C. mechowi; 0.74+/-0.06 cm3 O2g-1 h-1 (n=8) for C. bocagei and 0.63+/-0.06 cm3 O2 g-1 h-1(n=21) for C. h. amatus. The thermoneutral zones (TNZs) of allthree species are narrow: 29-30-degrees-C for C. mechowi; 31.5-32.5-degrees-C for C. boeagei, and 28-32-degrees-C for C. h.amatus. The increase in mean RMR at the lowest temperaturestested (15-degrees-C for C. mechowi, 18-degrees-C for C.bocagei and C. h. amatus) was 2.35, 2.2 and 3.82 times theirRMR in the TNZ respectively. Body temperatures are low, 34+/-0.53-degrees-C (n=24) for C. mechowi, 33.7+/-0.32-degrees-C(n=20) for C. bocagei and 33.8+/-0.43-degrees-C (n=40) for C. hamatus. At the lower limit of thermoneutrality, conductancesare 0.09+/-0.01 cm3 O2 g-1 h-1-degrees-C-1 (n=30) in C.mechowi; 0.12+/-0.01 cm3 O2 g-1 h-1-degrees-C-1 (n=20) in C.bocagei and 0.12+/-0.03 cm3 O2 g-1 h-1-degrees-C-1 (n=32) in C.h. amatus. The range in mean body mass among the seven speciesof Cryptomys examined for scaling was 60 g (C. darlingi) to 267g (C. mechowi). There is no clear relationship between RMRwithin the TNZ and body mass. The resultant relationship isrepresented by the power curve RMR=2.45 mass-0.259.