OBJECTIVES: To examine patterns of use of hormone therapy (HT), including duration of use, in North Norway in 1996, 2002 and 2005. METHODS: Within the NOWAC cohort we conducted a cross-sectional comparison of questionnaire data among women aged 48-62 years in 1996 (N=8822), 2002 (N=6262) and 2005 (N=4830). Response rates for first time respondents: 58% in 1996 and 66% in 2005. The 2002 participants were second time respondents including 4814 of the 1996 participants. The partial dependence was managed statistically using generalized estimating equations (GEE) and linear mixed models. RESULTS: Use of HT increased from 1996 (30.5% current, 43.3% ever) to 2002 (38.2% current, 59.3% ever), and decreased toward 2005 (14.7% current, 35.8% ever). High-dose combinations were still the most used HT products in 2005, although low-dose estrogen products and tibolone had gained market shares. Current use of HT among pre-/perimenopausal women was 9.4% in 1996, 13.2% in 2002 and 0.6% in 2005. Mean duration of current HT use was 3.7 years in 1996, 5.8 years in 2002 and 6.3 years in 2005 (p