The acquisition of reliable beam data is essential to the process of commissioning a radiotherapy system. Regardless of the treatment planning software used, the ability to acquire accurate beam data is fundamental. This course is designed for the clinical physicist looking to gain knowledge and experience scanning linear accelerator beams. Photon beams are emphasized, including special considerations when working with flattening filter free (FFF) beams and small fields. The course also covers detector (ion chamber) selection and set up, quality assurance considerations, and evaluating beam data, i.e. the characteristics of a good profile and how to spot it in the data when a machine is not properly tuned. The course incorporates hands-on time in an accelerator lab, with practice acquiring high quality PDD, profiles, and point measurements along with TMR, DLG, and small field measurements in a water tank.