Introduction: Since the foundation of the German Hodgkin Study Group (GHSG) in 1978 a central radiotherapy (RT) reference centre was established to evaluate and to improve the quality of treatment. During the study generations the quality assurance programs (QA) were continuously adapted and refined. The purpose of this analysis is to show the results of the work within the fifth study generation (HD13/14) and to demonstrate the establishment of a QA including modern RT-techniques e.g. intensity modulated RT (IMRT), image guided RT (IGRT) and involved node RT (IN-RT). Methods: With the fourth study generation (HD10-12) a central prospective review of all diagnostic imaging to create an individual treatment plan for every study patient was established in early stages and the quality of involved field RT was evaluated by an expert panel of radiation oncologists retrospectively. In the era of modern conformal RT this QA-program had to be adapted fundamentally and within several meetings a new process of evaluation has been developed. The findings were compared to the results of the QA within the fifth study generation (HD13-15). Results: The expert panel analyzed the RT-parameters of 1037 (28%) patients (HD13 n=465, HD14 n=572). In 85% simulation films and in 87% verification films were available. RT was assessed as unacceptable in 46% (HD13= 38%, HD14=52%), acceptable in 9% (HD13= 9%, HD14= 9%) and according to the protocol in 45% (HD13= 52%, HD14= 38%). These findings were compared to a data set of eleven patients treated within the sixth study generation (HD16-18) which was reviewed using the “new” revised QA-program including criteria for conformal techniques. Conclusion: The value for QA of RT within the GHSG trials is well known. To develop a QA-program of modern RT the expert panel defined criteria for analyzing current RT-procedures. With this schedule the QA of the GHSG serves as a model for other study groups.