Covering the head was associated with significant increases in heart and respiratory rates, and periph- eral skin temperature in both body positions and at both ages except for heart rate at 5 months when sleeping supine (Table 3). There was a minor, but significant increase in transcutaneous Pco2 after cov- ering during prone sleep at both ages, and transcu- taneous Po2 was higher after covering in both posi- tions at 21⁄2 months (Table 3). Comparing prone and supine sleep when the head was covered, prone was associated with a higher mean heart rate at both ages, and a higher mean peripheral skin temperature and transcutaneous Po2 at 21⁄2 months, but there were no significant differences in transcutaneous Pco2 or oxygen saturation (Table 3). With increasing age, heart and respiratory rates decreased signifi- cantly for both positions before and after covering, and peripheral skin temperature was significantly lower during prone sleep after covering at 5 months. There were no differences with age for other param- eters. The skin on the trunk and face of all but four infants was warm upon touch when the cover was