Radiation planning for cancer therapy is becoming more and more dependent on the prediction of microscopic tumor spread to regional lymph nodes for its success. It is known that microscopic spread tends to follow established lymphatic drainage pathways in the head and neck based on the location of the primary tumor. In this paper,we propose a novel model for the prediction of regional lymphatic involvement of head and neck squamous cell carcinoma based on primary tumor location and T-stage. The proposed model operates from first anatomical principles and basic stochastic techniques, and is validated against surgical data.