Chlamydia is a potentially damaging sexually transmitted disease, affecting hundreds of thousands of people - both men and women - in Britain. If untreated, it can cause acute pain and damage the fallopian tubes irreparably, leaving women infertile. Yet it can be easily and cheaply treated with antibiotics once the infection is diagnosed. Alison Holt reports on the lack of awareness of this condition and asks why there has been no national research into the size of a problem that was identified in the mid-seventies.