Objective: To investigate differences in demographics, strength and sensory system function of 254 women aged 40-80 years categorized as stable, unsteady or unstable using simple balance tests. Method: Demographics (age, height, weight, medications, co-morbidities, falls history, activity level), measures of quadriceps, hip abductor and adductor strength, somatosensory, visual and vestibular function were recorded. Subjects were categorized as stable (completed all trials), unsteady (failed one/two trials) or unstable (failed all trials) after three 10-s trials of bilateral stance (foam surface, eyes closed (EC)) and one-leg stance (firm surface, eyes open (EO)), and the results were compared. Results: Both balance tasks identified women in their fifties as unstable (∼9%), with 60% of these women failing both tasks. More women were unsteady or unstable on foam EC (27%) than in one-leg stance EO (20%). Unsteady and unstable categories of women were older, reported more co-morbidities and medications and less activity than stable women. The women categorized as unstable in either test recorded weaker hip muscles, higher vibration thresholds, greater joint positioning error, reduced edge contrast sensitivity, low-contrast visual acuity and reduced dynamic visual acuity than the stable categories (p<0.01). The two tests detected differences in characteristics of unstable women, with those failing one-leg stance EO being heavier, and those failing foam EC having weaker quadriceps. Conclusion: These data link instability in women from the fifties to multiple demographic and sensorimotor factors associated with increased risk of falls, thus supporting use of balance tests in primary-care settings to assist referral for diagnostic assessment and pre-emptive interventions.