Isolation of nontuberculous mycobacteria (NTM) from the sputum of individuals with CF is an increasingly common finding, and the lack of an evidenced-based approach to treatment of NTM disease has been identified as one of the greatest unmet needs within the CF community. Current evidence predicts that the prevalence of NTM will remain relatively high in the CF population. Approaches to NTM disease treatment differ widely between centers, and expected outcomes are not known. This study is observational and follows current best practices. The study will help define response to treatment, and collect relevant data associated with treatment of NTM disease to build a framework for future therapeutic trials.

Inclusion Criteria:

1. Previous participation in PREDICT and diagnosis of NTM disease for the same species of NTM
2. Intention to treat for NTM disease for M. avium complex or M. abscessus complex
3. Written informed consent (and assent when applicable) obtained from participant or participant's legal representative
4. Signed informed consent to participate in data submission to the CFF Patient Registry
5. Be willing and able to initiate treatment for NTM and to adhere to study procedures in the context of clinical care, and other protocol requirements

Exclusion Criteria:

1. Pregnant or breastfeeding
2. Has any other condition that, in the opinion of the Site Investigator/designee, would preclude informed consent or assent, make study participation unsafe, complicate interpretation of study outcome data, or otherwise interfere with achieving the study objectives

Male and female subjects with CF age 6 years and older with a confirmed diagnosis of NTM disease who are initiating treatment for NTM.