The number of new cases of sexually transmitted infections (STIs) has dropped for the first time in a decade.
Figures from the Health Protection Agency (HPA) show a small 1% drop across England in 2010, especially among young people.
There were 418,598 new STI diagnoses in 2010, down 1% on the 424,782 cases in the previous year.
The decline is against a backdrop of increased testing for STIs (up 1% in a year to 1.18 million tests in 2010).
Cases of chlamydia, which is particularly common among under-25s, remained stable at 189,625 cases in 2009 and 189,612 in 2010.
There were 2.2 million chlamydia tests among 15 to 24-year-olds in 2010, an increase of more than 196,000 (10%) from the previous year.
Genital warts diagnoses also fell 3%, from 77,900 in 2009 to 75,615 in 2010. Cases of syphilis fell 8%, from 2,846 in 2009 to 2,624 in 2010, and genital herpes dropped 8%, from 27,564 cases in 2009 to 29,703 in 2010.
According to the HPA, it is too early to say exactly why the numbers are falling. One possibility could be that regular testing is preventing infections being passed on.
Terrence Higgins Trust Chief Executive Sir Nick Partridge said: "The decreases in STIs that we saw in 2010 are small, but very significant. We're finally beginning to see a slowing down in the rates of infections, particularly among young people, showing that the time and money that has been put into sexual health, and in particular chlamydia screening, in recent years is starting to pay off.
"We are at a vital tipping point but, with the national sexual health strategy of the last ten years now expired, Government leadership and local investment are crucial. Over 400,000 people were treated for an STI in England last year. We need to provide accessible, targeted and community based sexual health services and prevention campaigns if we are to maintain the momentum in bringing these figures down."