Acupuncture may be an effective way of easing severe period pain, a South Korean review of 27 studies suggests.
Researchers said there was "promising evidence" for acupuncture in treating cramps, but that more work was needed.
In the British Journal of Obstetrics and Gynaecology, they noted two studies found little difference between real and sham acupuncture in treating pain.
Acupuncture is a less contentious form of complementary medicine than some, but its value is still disputed.
Period pain can be severe in some women and may be accompanied by nausea, diarrhoea, migraine and backache. Common treatments include pain killers, applying heat and exercise - although a recent study questioned the efficacy of the latter.
This latest review involved 27 studies - which included nearly 3,000 women. They addressed a variety of forms of acupuncture - from classical to acupoint injection.