Multiple studies have examined the quality of life of cancer patients before or after treatment, but few have evaluated the impact of a specific course of treatment on cancer patients' quality of life. Using a longitudinal design, we examined the quality of life of 24 women and 8 men before receiving their initial course of chemotherapy and again at 21 days after the first course of chemotherapy. The study was carried out at the outpatient chemotherapy unit of a university hospital located in the city of Izmir, West Turkey. Research data were collected using a patient demographic form and the Rolls Royce Model Quality of Life Scale. All of the postchemotherapy mean scores from the quality-of-life instrument were statistically significantly lower at day 21, except for the cognitive functioning subscale. Overall, initial chemotherapy was found to have a significantly negative effect on the quality of life of cancer patients. Nurses can help patients prepare for an initial decrease in their quality of life early in treatment.