About half of all nail diseases are caused by onychomycosis, a fungal infection of the nail caused by dermatophytes, yeasts, and non-dermatophyte moulds. There is some evidence that nail dermoscopy is a valuable diagnostic and follow-up technique for onychomycosis. Patients with onychomycosis who are taking oral terbinafine (250 mg) for six weeks will have their dermoscopic alterations evaluated. 30 Egyptian patients with clinical and mycological diagnosis of onychomycosis were included in this study. They were picked from the dermatology out-patient clinic, Dermatology Department, Benha University Hospitals in Egypt for the study. Direct microscopy with 20% potassium hydroxide (KOH) and fungus culture on Sabouraud dextrose agar medium and nutritional agar media were used to evaluate all nail specimens. Pre- and post-treatment polarised noncontact dermoscopic examinations with oral terbinafine (250 mg) were performed using the dermoscope. Results: KOH was positive in all of the patients. 56.7 percent of the samples were positive for T. Rubrum, 20 percent for T. Mentagrophyte, 13.3 percent for Aspergillus Niger, 6.7% for Candida, and 3.3% for Aspergillus Flavus. Distolateral subungual onychomycosis (DLSO) was the most prevalent form (73.3 percent ). Terbinafine was given to all patients (250 mg). Thickness, subungual hyperkeratinization, periungual inflammation, and dystrophy (P 0.001) were all significantly improved as compared to baseline data. With each successive follow-up period (P=0.001, P=0.001, P=0.001, P=0.001, P=0.001, P=0.001), the aurora pattern, onycholysis, jagged distal edge, spike pattern, uneven distal termination and longitudinal stria frequencies progressively improved. As a result, dermoscopy is a rapid, noninvasive, and helpful method for diagnosing onychomycosis and monitoring its progress after therapy.