Blood and plasma viscosity, as well as erythrocyte filtration rates were studied in 44 osteopenic (20 men and 24 women) and in 40 non-osteopenic (20 men and 20 women) patients, all over 65 years of age. Pathological hemorheological parameters were observed only in 12 subject of the osteopenic group, and 10 controls. The results indicate that although the hemorheological parameters do not show a direct correlation with the osteopenia, it is worthwhile following these parameters, among others, in order to optimize the treatment with anti-osteoporotic drugs which are able to regulate them.