The human sweating response is subject to the influence of diverse classes of drugs. Some act centrally at the hypothalamus or at spinal thermoregulatory centres, while others act at sympathetic ganglia or at the eccrine-neuroeffector junction. Pharmacological disturbances of sweating have broad clinical implications. Drugs that induce hyperhidrosis, or sweating in excess of that needed to maintain thermoregulation, can cause patient discomfort and embarrassment, and include cholinesterase inhibitors, selective serotonin reuptake inhibitors, opioids and tricyclic antidepressants. Drugs that induce hypohidrosis, or deficient sweating, can increase the risk of heat exhaustion or heat stroke and include antimuscarinic anticholinergic agents, carbonic anhydrase inhibitors and tricyclic antidepressants. As acetylcholine is the principal neuroeccrine mediator, anhidrosis is one of the clinical hallmarks by which acute anticholinergic toxicity may be recognized. The symptom of dry mouth often accompanies the less apparent symptom of hypohidrosis because the muscarinic M(3) acetylcholine receptor type predominates at both sweat and salivary glands. Management options include dose reduction, drug substitution or discontinuation. When compelling medical indications require continuation of a drug causing hyperhidrosis, the addition of a pharmacological agent to suppress sweating can help to reduce symptoms. When hypohidrotic drugs must be continued, deficient sweating can be managed by avoiding situations of heat stress and cooling the skin with externally applied water. The availability of clinical tests for the assessment of sudomotor dysfunction in neurological disease has enhanced recognition of the complex effects of drugs on sweating. Advances in the understanding of drug-induced anhidrosis have also enlarged the therapeutic repertoire of effective treatments for hyperhidrosis.