This is a prospective, multicenter open-label study in adults with CF who are colonized with NTM. Subjects will receive two 5-day infusion cycles of IV gallium. The study will evaluate the safety and antimycobacterial effect of two 5-day infusions of IV gallium. Subjects will be on study for up to 148 days, with a screening period of up to 7 days and active study period up to 20 days. About 40 people with CF who are 18 years of age or older will take part in this study at about 10 hospitals and clinics around the country.