Safe mobility is important for quality of life of older people while mobility limitation may lead to loss of autonomy and further deterioration of health. Mobility is typically assessed first of all with tests on maximal or customary walking speed over shorter distances or walking endurance over longer distances. Self-reports of perceived difficulty walking particular distances are commonly used in epidemiological studies. Using data of the Finnish Twin Study on aging, we found that 20-50 % of individual differences in walking speed and walking endurance are explained by genetic factors among older women. Other factors underlying poor mobility which we have analyzed in our data include poor strength and balance, overweight and obesity, sensory deficits such as poor vision and hearing, falls, pain, fear of moving outdoors, sedentary behavior and negative environmental features. People with mobility limitation often suffer from unmet need for physical activity manifested as perceiving no opportunity to participate in exercise even though would want to do so. We carried out a randomized controlled trial on physical activity counseling among 632 community living people aged 75-81 years who were at most moderately active, had no apparent memory problems and who at baseline were able to walk at least minimally. The experimental group received a single face-to-ace counseling session followed up with supportive telephone contacts every for months for two years. Data on perceived difficulty walking 500 m and 2 km were collected every six months for the two year study period as well as one and half year follow-up after the end of the intervention. Intervention group developed statistically significantly less difficulties in 2 km walk than control group. Results for 500 m walk parallel but remained non-significant. Behavioral interventions may be useful in preventing development of mobility limitation in old age. More research is needed on sustainable ways to promote mobility in old age.