Objective: There has been controversy about the results of the Women's Health Initiative and the Million Women Study and uncertainty about their impact on hormone therapy (HT) use. This study documents recent trends in HT use in postmenopausal women in the United Kingdom.Design: Between April 2001 and September 2005, 202,638 postmenopausal women aged 50 to 74 and with no history of bilateral oophorectomy were recruited to the United Kingdom Collaborative Trial of Ovarian Cancer Screening. The proportion of women randomized each month who were using HT was calculated. The trend in HT use was assessed with reference to the publication of the Women's Health Initiative interim results (July 2002), the Million Women Study (August 2003), and advice from the UK Committee on Safety of Medicines (December 2003).Results: The median number of women recruited and randomized per month was 3,955 (mean 3,744). The proportion of randomized women using HT between April 2001 and June 2002 was 29%. This was followed by a steady monthly decline, and by February to September 2005, only 10% to 11% of newly recruited women were using HT. This trend was present in all age groups. However, in current users, the average duration of HT use remained steady at 10 to 11 years.Conclusions: There was a steady decline in HT use among postmenopausal women at recruitment into the United Kingdom Collaborative Trial of Ovarian Cancer Screening between April 2001 and September 2005. This is likely to reflect general trends in the UK population and is probably related to the premature closure of the large HT trials and the ensuing publicity.