Assessment of coral disease prevalence was carried out in six islands in the northern region of the Gulf of Mannar during February 2007. Assessment was made in two sites in each island and three transects were laid in each site. white band, white plaque, white spot, pink spot, black spot, black band, yellow spot, yellow band and tumors were the observed common diseases in this regime. Overall coral disease prevalence was 8.9%. Prevalence was highest at Poomarichan Island (10.90%), followed by Manoli (9.38%), Pullivasal (9.28%), Hare (8.64%), Krusadai (8.27%) and Shingle (6.82%). Most common disease was pink spot in Porites sp followed by black band in Porites sp., Pocillopora sp., Favia sp., and Favites sp. Tumors were also observed in low frequencies in Acropora cytheria. Other affected species were Acrpora cytherea, Favia pallida and Goniastrea sp. Present study also consists the frequency of temperature anomalies, which can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant both in cover and diversity.