This study investigated, in a convenience sample of 279 patients with cancer, the trajectories of symptoms and loss of physical functioning over time, the relationships of these variables to age and co-morbidity, and differences existing according to cancer site (breast, lung, colorectal/gastrointestinal, urinary/reproductive, lymphoma, and "other"). The patients were surveyed twice; at intake (wave I, n = 279) and 6 months later (wave II, n = 160). Findings indicated, at wave I, that age and co-morbidity were significantly correlated, and loss of physical functioning was associated primarily with symptoms and, to a lesser degree, with age. Loss of function scores varied significantly according to cancer site, with higher levels for patients with lung cancer and lower levels for patients with breast or colorectal/gastrointestinal cancer. The most frequently occurring symptoms were fatigue, insomnia, pain, and nausea. Average levels of symptoms and loss of physical functioning were lower at wave II, indicative of a possible treatment-related effect (at wave II, a smaller percentage of patients had recently undergone treatment). Although co-morbidity was only modestly correlated with symptoms and loss of function for the total sample, it was highly correlated with both symptoms and loss of physical functioning for the younger patients (those younger than 60 years of age). The significant link that was identified between symptoms and loss of physical functioning has important implications for physicians, nurses, and other healthcare providers caring for patients with cancer as they deal with symptom management and quality-of-life issues.