A retrospective study of 40 women with carpal tunnel syndrome developing in pregnancy and 18 women with carpal tunnel syndrome in the puerperium was undertaken. All the cases that developed in pregnancy occurred in the third trimester and resolved within two weeks of delivery. Those cases developing in the puerperium affected women who had breast-fed their infants and their symptoms lasted a mean of 5.8 months. These patients were older and more likely to be primiparous than if the condition occurred in pregnancy. All the pregnant women and none of the lactating women had symptoms of peripheral oedema. Spontaneous resolution with a good response to conservative measures occurred in both groups; only three cases were treated surgically. Residual clinical evidence of median nerve damage was present in 40% of all cases. Carpal tunnel syndrome which develops in pregnancy appears to be a separate clinical entity to that developing in the puerperium.