Hot flushes are experienced in those periods of the female life when estrogen levels are low. Hormone replacement therapy is thus the first choice for treatment of hot flushes. However this treatment is not always accepted or contraindicated for a variety of reasons. Estrogen (and progestogen) strongly interact with a number of neurotransmitters and this has led to a range of non-hormonal treatments including compounds that act via the noradrenergic or dopaminergic systems as well as herbal remedies. These treatments (which are shortly reviewed) are not always successful. Surprisingly, apart from treatment with some selective serotonin (5-HT) reuptake inhibitors (SSRI's), up till now, little attention is given to the strong interaction of estrogens with the serotonergic system. These interactions are shortly reviewed. Based on these interactions, a hypothesis on the genesis of hot flushes is postulated. Especially the 5-HT(2A) receptor subtype may play a key role in the occurrence of hot flushes. A number of arguments that support this hypothesis are discussed.