 - Have had up-to-date screening tests for cancer as recommended by the American Cancer Society. These tests include a PSA blood test for prostate cancer for males over age 45, a pap smear for cervical cancer for females, a mammogram for females over age 40, and a flexible sigmoidoscopy for colon cancer if over age 50. To be in this study, you must have written proof of normal test results within the last 12 months. If these screening tests show you have cancer, you will not be able to be in the study. 