1 The physiology of piloerection is described and clinical experience is discussed.
2 The objective and subjective evidence for drug-induced piloerection by a number of drugs is given and, where it is known, their pharmacological mechanism is described.
3 The results are considered in relation to the hypothesis that drug-induced piloerection is only produced by drugs with α1-adrenoceptor agonist activity. For those drugs without the latter activity where piloerection is supported only by subjective evidence it is suggested that objective evidence should be sought.
4 The fact that there is no objective evidence that the classical α1-adrenoceptor agonist, phenylephrine, produces piloerection is found surprising and it is suggested that such evidence should be sought. If it is found that phenylephrine does not produce piloerection, then the possibility of the existence of a further α-agonist subgroup needs to be considered.