The aim of this study was to determine if radiotherapy induces hyposalivation altering oral microbial flora. The purpose of this placebo-controlled, single-blind study was to determine beneficial effects of a saliva substitute and an oral hygiene product on irradiated patients with oropharyngeal cancer. Eighteen patients were assigned to the test group (Biotène Oral Balance gel [Lacléde Incorporated Healthcare Products, Gardena, CA] and toothpaste used daily), and another 18 were put on a conventional daily regimen (carboxymethylcellulose gel and Oral-B toothpaste [Laclede Pharmaceuticals, Gardena, CA]). Cultures for identifying and quantitating microorganisms, whole unstimulated saliva, and visual analog measurements for comfort were obtained before mucositis occurred and after treatment. Daily use of Biotène products enhanced control of microbial flora, improved salivary flow, and increased oral comfort as compared with control subjects. Four weeks after mucositis, some aerobic isolates disappeared in the test group; periodontal-associated bacteria were markedly decreased in the test group; and candidal species were significantly lowered in the test group. Although baseline saliva was lower in the test group (P = 0.001), after 4 weeks, no difference between groups existed; comfort was greater in the test group (P = 0.007). Use of enzyme-engineered Biotène products that assist in control of the oral microbial flora as well as supporting oral comfort through lubrication appear to be useful aids for irradiated patients with oropharyngeal cancer.