In search of evidence for or against the endothermic dinosaur hypothesis, a recent study by Ruben et al. (1996) revealed that endotherms tend to have larger nasal cross-sectional areas than ectotherms of the same mass. The reason offered for this observation was that larger nasal passages are needed to house the complex respiratory turbinates possessed by endotherms. Whales were excluded from the study on the grounds that they have no nasal turbinates. In the present study, the cross-sectional area of the nasal passages of nine species of Odontoceti were measured by the use of latex casts. The regression of log cross-sectional area vs. log mass yielded the same line for the whales of the current study as for the endotherms of the previous study. Alternative explanations for the large nasal cross-sectional area of endotherms are sought.