We enrolled a cohort of 303 stage I or stage II breast cancer patients diagnosed in Boston, MA, between October 1992 and December 1995. We followed the patients by interview and medical record abstract for 5 years (a) to characterize the incidence and predictors of upper-body function decline and (b) to characterize the incidence and predictors of recovery of upper-body function. The incidence of decline in the first year after therapy (17.7/100 person years) was substantially higher than in the subsequent 4 years of follow-up (11.0/100 person-years, p value for test of homogeneity equal 0.028). With only one exception, no patient characteristic, therapy component, or disease trait was associated with decline over the full follow-up period. Women with less than a high school education had an adjusted relative hazard of decline of 2.3 (95% CI, 1.4-3.7) compared with women with a high school education or more, possibly reflecting occupational or environmental insults that predispose to functional impairment. Women who had reported a decline in upper-body function and who subsequently saw their breast cancer specialist were 4.8-fold more likely to report that they had recovered their upper-body function at their next interview (95% CI, 2.0, 12). This finding suggests that attention to upper-body function during follow-up visits may facilitate recovery.