1. A series of 152 patients with primary nasopharyngeal cancer from the Head and Neck Unit of the Royal Marsden Hospital was analyzed and the natural behavior of their tumors studied. The ratio of male to female was 2.1:1. The ratio of undifferentiated carcinoma to squamous cell carcinoma was 2.4:1. The ratio of male squamous cell carcinoma to female squamous cell carcinoma was 1.9:1. The ratio of male undifferentiated carcinoma to female undifferentiated carcinoma was 2.2:1 The ratio of male undifferentiated carcinoma to male squamous cell carcinoma was [See Table in the PDF] 2.5:1. The ratio of female undifferentiated carcinoma to female squamous cell carcinoma was 2.3:1. 2. The peak incidence was in the fifth and sixth decades, but the peak survival rate was in the fourth decade, females having a higher survival rate than males and patients with undifferentiated carcinoma having a higher survival rate than patients with squamous cell carcinoma. No patient in the first or second decade survived. 3. The most frequent initial site was the posterosuperior wall in which also the lowest survival rate was noted. 4. The most frequent presenting symptoms were nasal and auricular, with no relationship to the survival rate. 5. Dividing the patients into 5 groups based on the delay of diagnosis in months, the highest incidence was found in Group 0 to 6 months. Correlating the delay with Stage, to obtain the relationship between time-delay and local extent of the tumor—a factor which the writer calls clinical age of the tumor—it is shown that T1 tumors have the highest proportion with 3 to 6 months delay, perhaps reflecting that they are rapidly growing and thus cause earlier symptoms. The tumors of T2 and T3 are more or less evenly distributed in all the delayed groups, perhaps reflecting an average growth pattern. Tumors T4 show a slight tendency towards a greater time-delay, possibly reflecting a very slow tumor growth pattern. When we correlate this stage-delay relationship with the 5 year crude survival, we obtain the lowest survival rate in the 0 to 3 month delay group and the peak in the 6 to 9 month delay group, remaining rather stable for the 9 to 12 and more than 12 month delay groups. Based on these criteria of the clinical age of the tumor, the cases in this series may be considered as having 3 kinds of tumors: a. Small tumors giving symptoms early and leading to demise of the patient rapidly; b. tumors with an average growth pattern, giving symptoms later and producing a longer survival; and c. tumors having a very slow growth pattern and thus producing a considerably longer survival. 6. Undifferentiated carcinomas showed a higher 5 year crude survival rate than squamous cell carcinomas, almost three times as high. 7. The peak incidence was in T3 tumors and the highest survival rate was in T1. Based on lymph node involvement the highest survival rate was in N0 tumors. Thus there was a close relationship between Stage, lymph node involvement and survival rate. Lymph node involvement, either bilateral or fixed, was present in 71.6 per cent of the patients. 8. The most frequently invaded areas were the oropharynx and nasal cavity, followed by spread superiorly to the base of the skull and the anterior prestyloid and retrostyloid parapharyngeal compartments. Tumors of the posterosuperior wall spread more frequently to the base of the skull. It is, therefore, advisable that the base of the skull, the posterior third of the nasal cavity, and a good portion of the oropharynx be included in the field when treating the primary tumor so as to cope with the possible spread to these areas, where it escapes us many times because of its submucosal infiltrating character. The patients with tumors spreading to the base of the skull had the lowest survival rate. This series of cases was treated almost entirely with orthovoltage and therefore is not comparable to modern series treated with supervoltage.