The effects of hormonal status and activity levels on Achilles tendon structure were examined in asymptomatic post-menopausal women. It was hypothesized that women using hormone replacement therapy (HRT) would have better tendon structure than those not using HRT and that active women would have poorer tendon structure than inactive women. Eighty-five women including 53 active women (regular golf players) and 32 controls (healthy but inactive women) recorded their HRT and menopausal history and underwent basic anthropometric measurements. Women were divided into two groups based on their hormonal status: those currently using HRT; and those who had never used HRT or ceased using HRT at least 12 months prior to the study. Achilles tendons were examined with ultrasound and categorized as normal or abnormal, and the diameter of each tendon (mm) was recorded. Active women had a greater prevalence of tendon abnormality (P=0.10) and thicker Achilles tendons than inactive women (P<0.05). Active women on HRT had less tendon abnormality (P=0.056) than active women not on HRT and significantly less tendon thickness (P<0.05). This study indicates that Achilles tendon diameter is greater in active post-menopausal women. Hormone replacement therapy appeared to ameliorate this effect in active women. A similar effect from HRT on the Achilles tendons of inactive women was not apparent.