Background: Allergic fungal rhinosinusitis (AFRS), the most common form of fungal rhinosinusitis (FRS) results from an allergy to fungus in immunocompetent patients. There is no consensus on the diagnostic criteria for AFRS and confusion prevails due to difficulty in demonstrating fungal hyphae in the mucin. Methods: We classified patients with FRS (n=30) using various clinical, histopathological and microbiological parameters. The patients underwent computed tomography of nasal and para-nasal sinuses, absolute eosinophil count and testing of serum immunoglobulin E levels. Fungal elements were identified in nasal lavage and polyp samples from 30 patients with chronic rhinosinusitis using potassium hydroxide (KOH), culture, histopathological examination, polymerase chain reaction (PCR) and were categorised into eosinophilic mucin rhinosinusitis, eosinophilic fungal rhinosinusitis, AFRS and fungus ball categories. Results: Allergic fungal rhinosinusitis was evident in 5 (20.8%) patients (EMRS 1; EFRS 4, based on histological examination). Diagnosing the aetiological agent in suspected cases of FRS requires not only a high index of clinical suspicion, but a thorough microbiological and pathological work-up of the samples also and should always be supported by computed tomography findings and immunological work-up for atopy as these not only constitute important diagnostic criteria in cases of AFRS, but also are important pre-operative predictor for the condition. Conclusions: Histopathological examination remains the gold standard for diagnosing chronic FRS but speciation can be possible only with culture or PCR on appropriate samples. The rapid methodology of PCR with appropriate primer pairs has shown promising results in our study and in collaboration with radiological and immunological work-up would provide the complete picture for the diagnosis of FRS.