Sex differences in factors related to subjective well-being were evaluated in people in their late old age by interviewing individuals aged 75 years and over living in 2 regions of Enzan City, Yamanashi Prefecture. The 17-item revised "Philadelphia Geriatric Center (PGC) Morale Scale" was used for evaluation of subjective well-being. Factors related to family status, employment, health related factors, activities of daily living, and results of physical examinations were each classified into two or more categories, and PGC Morale Scale points were compared among the categories for all subjects and separately for males and females using the Mann-Whitney test and the Kruskal-Wallis test. 1) Although the mean age of males (80.0 +/- 4.4 years) and females (80.4 +/- 4.3 years) was no significantly difference, PGC Morale Scale points were significantly higher in males than in females (p < 0.05), indicating a sex difference in subjective well-being. 2) In elderly females, subjective well-being was related to many factors, and there was a particularly strong relationship between subjective well-being and both health related factors and activities of daily living. 3) In elderly males, the factors related to subjective well-being were fewer than in females, consisting only of "social opportunities", "hobbies", and "grip strength". Since factors related to subjective well-being differ between the sexes, these differences must be taken into account when evaluating subjective QOL of the elderly.