This longitudinal and prospective study aimed at investigating the influence of some parameters,including nasal cytology and clinical findings (such as asthma, atopy, acetylsalicylic acid (ASA) sensitivity, ASA associated with asthma), as risk factor of post-surgical relapse of nasal-sinus polyps. One hundred sixty-one consecutive patients (92 males and 69 females, mean age 47 years), affected by bilateral nasal polyposis and who had undergone surgical nasal polypectomy (endoscopic FESS), were examined post-surgically at least every 6 months for a period of 10 years. Endoscopic exam and nasal cytology exam were carried out on all patients and their case histories were carefully examined. The association eosinophilic-mast cell cellularity and the contemporary presence of asthma + ASA sensitivity showed the highest level of relapse (OR 4.5). In conclusion, cytological data in association with certain clinical parameters can predict a high risk prognosis of relapse.