The primary aim is to test the combined effectiveness of OMT and targeted head exercise (THE) to achieve a significant decrease in headache measures of frequency, intensity, and duration in a Treatment group when compared to a Control group whose members receive only standard medical care. A parallel, 2-arm, longitudinal, randomized controlled trial (RCT) will focus upon female patients (18 to 75 years of age) who have been diagnosed with chronic cervicogenic headache (CeH) based upon a differential diagnosis that includes classification according to the International Headache Society Classification IHSD 3rd Edition, reproduction of referred headache resulting from manual pressure over the upper cervical regions, and objective MRI findings. It is estimated that a sample size of 30 will provide sufficient statistical power (79%) to detect an intervention effect that corresponds to a clinically meaningful recovery (60%). CeH is classified as a secondary headache disorder because the headache pain is a consequence of injury to, or disease of, the bony and/or soft tissues of the upper cervical spine. It has been reported that some patients diagnosed with CeH demonstrate atrophy and/or fatty infiltration (FI) of the RCPm muscles on MRI. FI and/or a reduction in the cross-sectional area (CSA) of active muscle would not be expected to be the direct cause of chronic headache, but either or both could prevent muscles from generating normal physiologic levels of force. It has been shown that there is a functional connection between the pain sensitive dura mater and RCPm muscles and it is known that mechanical stretching of the dura mater results in referred headache. While FI and/or a reduction in the CSA of active muscle would not be expected to be the direct cause of chronic headache, it is known that muscle pathology will result in functional deficits. It is proposed that pathology in RCPm muscles will compromise the normal functional relationship between the RCPm and the dura mater and result in referred head and neck pain. It is predicted that at the end of the study, the Treatment group will show a significant decrease in headache measures that will be accompanied by a significant increase in CSA and a significant decrease in FI on MRI, and restoration of a normal head posture that will not be seen in the Control group. The proposed study is unique in that we are proposing both a mechanism and a source for some instances of CeH. By testing the effectiveness of specific interventions to address a specific pathology within a specific headache population, and by restricting the study cohort to female subjects presenting with CeH, this study will increase the ability to detect a significant change in the outcomes by increasing the power of the statistical analysis.