The presence of excess nasal mucus causing noisy nasal breathing with an obvious mucus discharge (snuffles) is a common problem in infants in the first three months of life. The presence of "snuffles" has traditionally been ascribed, unproven, to an upper respiratory tract infection despite there being no other signs of an acute infection in the majority of infants with "snuffles". To assess the possible role of impaired vasomotor control (autonomic function) in the pathogenesis of snuffles we measured the effect of a change from the supine to the upright position on resting blood pressure in 50 infants with "snuffles" and 50 healthy control infants. The mean age in both groups was 7 weeks post delivery, all infants were attending a well baby clinic for a routine examination, had no signs of an acute infection and none were on any medication (including nasal drops). A fall of greater than 10% of resting blood pressure was taken to indicate postural hypotension. Four of fifty infants in the control group compared to 22 of 50 in the snuffles group demonstrated postural hypotension (Chi square 16.84, p less than 0.001). The results suggest that in some infants "snuffles" may be associated with impaired vasomotor control.