Excellent local control rates of interstitial brachytherapy in oral cavity cancer and oropharyngeal carcinoma have been demonstrated in different retrospective studies. Compared to external-beam radiation therapy the high local control rates with a low rate of side effects obtained by interstitial brachytherapy are the result of a steep dose reduction in the implant-surrounding normal tissues. Therefore, interstitial brachytherapy offers rather the possibility to give high doses without inevitably leading to high complication rates. Low-dose-rate (LDR) and pulsed-dose-rate (PDR) interstitial brachytherapy with 0.4-0.55 Gy/h/24 h for tumors of the oral cavity and oropharynx in selected patients is a proven, effective and safe treatment method with excellent long-term data both as a sole treatment modality and a postoperative method, as well as a unique treatment method of head and neck tumors in previously irradiated areas. This paper deals with the technical aspects of interstitial brachytherapy, that seem to be relevant to high-quality outcome, and gives an overview of indications as well as past and recent results of interstitial brachytherapy in head and neck cancer.