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The table below summarizes the available evidence on the risks and benefits of hormone therapy. Included are all randomized trials and meta-analyses looking at disease incidence or mortality. Inclusion of observational trials was dependent on size: case-control studies with 500 or more cases of the disease and cohort studies with at least 2,000 women are included here.

The year noted is when the study results were published. The name following the title of the study is the last name of the first author on the publication.

E = estrogen; P = progestin

Year	Study	Study Type	Participants	Hormones	Results	Other Notes
1996	Nurses' Health Study, Grodstein (B)	Cohort	112,593	E, E + P	Current use increases risk of pulmonary embolism 111%	No distinction between E and E + P; up to 16 years follow-up; no increased risk associated with past use
1998	Heart and Estrogen/progestin Replacement Study (HERS), Hulley	Randomized	2,763	E + P	Increases risk 189%	Average follow-up 4.1 years
2000	Estrogen in Venous Thromboembolism Trial, Hoibraaten	Randomized	140	E	Increased risk of recurrence	Participants had prior history of blood clots; trial stopped early with 10.7% recurrence in treatment group and 2.7% recurrence in placebo group
2002	Miller	Meta-analysis	12 studies: 3 randomized, 9 observational	E	Current use increases risk 214%
2002	Heart and Estrogen/progestin Replacement Study (HERS II), Hulley	Randomized	2,321	E + P	Increases risk 108% overall (6.8 years)	2.7 year extension of HERS with subset of participants from original study; 6.8 years total follow-up
2002	Women's Health Initiative	Randomized	16,608	E + P	Increases risk 111%	5.2 years follow-up