This research intends to evaluate the effect of exercise as an alternative method of improving mood in people with MS or SCI who are 45 years of age or older. All study participants will be asked to complete phone interviews with research staff four times over the course of the study.

Participants will be assigned to one of two approaches to physical activity treatment. People assigned to the Treatment A group will participate in a phone call with a study counselor to design a home exercise program based on his or her needs and abilities. Those in the Treatment A group will also receive 6-8 follow-up phone sessions. The Treatment B group will participate in an educational phone session with the study counselor, to discuss reasons to exercise and examples of exercise tailored to their disability.

All participants will also be asked to wear a device called an accelerometer to measure physical activity for three one-week periods. All study participants will receive up to $120 for their time and phone expenses.

You may be eligible for the study if:

• You are at least 45 years old.
• You spend less than 2 � hours per week in moderate physical activity.
• During the past two weeks you have felt either: Down, depressed or hopeless OR you have little interest or pleasure in doing things you normally enjoy.