Background/Objectives:The need for dietary counselling and nutritional support in oropharyngeal cancer patients is generally accepted. However, evidence for the effectiveness is sparse. The aim of this study was to describe dietary counselling, nutritional support, body weight and toxicity during and after treatment, and investigate the effect of pre-treatment body mass index (BMI) on survival in oropharyngeal cancer patients.Subjects/Methods:A retrospective chart review was made in 276 oropharyngeal cancer patients treated with radiotherapy (RT). End points were dietary consultations, weight loss, toxicity, overall survival and disease-free survival.Results:Almost all oropharyngeal cancer patients received dietary counselling (94%) and nutritional support (99%). Dietary counselling decreased sharply shortly after treatment to 38% at 1 year after treatment. Overall weight loss increased during the first year of follow-up and ranged from 3% at start of RT, until 11% at 1 year after RT. Overall survival was significantly longer for patients with a BMI above average (P=0.01). Acute dysphagia (P=0.001), mucositis (P=0.000) and toxicity grade 3 (P=0.002) were significantly more prevalent in patients who had lost 10% or more of their body weight.Conclusions:This study showed that patients continue to lose body weight during and until 1 year after treatment, despite nutrition support and frequent dietetic consultation. A BMI above average appears to increase survival time. Future studies, preferably randomized trials, are needed to compare standard dietary counselling with more intensive dietary counselling that consists of earlier and/or prolonged treatment.