Disability prevalence among men and women are investigated using NLTCS surveys conducted in 1982, 1984, 1989, 1994 and 1999 in the US population, on persons older than 65 years, and data from LSADT surveys conducted in 1995, 1997, 1999 and 2001 in the population of the Danish Twins Registry, on persons older than 75 years. In both surveys women are more disabled than men. The probability of becoming disabled and surviving is higher for women than men. The probability of recovering from a disability differs between the sexes statistically insignificant. No time trends are observed in the probabilities of becoming disabled, reversing disability or dying disabled. Calculations show that a decrease in disability prevalence observed in the USA resulted from a decrease in disability prevalence in ages younger than 65 years. Using LSADT data heritability of disability in women older than 75 years is estimated to be 36% (14%; 54%). In men of the same ages the estimate is 11% (0%; 40%) and for both sexes heritability is estimated at 28% (10%; 45%).