The intention of this study was to detect leptospirosis in suspected pyrexia cases with unidentified sanitary status in and around Chennai. A total of 458 serum samples from human were screened for presence of Leptospira antibodies. Of these, 176 serum samples were found positive for Leptospira antibodies and yielding an overall seropositivity of 38.40% with anicteric leptospirosis (87.4%.). Higher rate of seropositivity has been reported during the period of October 2008 to February 2009 and male comprise 62.00%. The occurrence of autumnalis was found to be 23.2%, icterohaemorrhagiae 21%, hebdomadis 12.6, australis 10.8%, grippotyphosa 9.7%, pomona 9%, copenhageni 6.9%, bataviae 4.6% and mixed 2.2% also found, though at lower frequencies. All the patients had fever and myalgia, head ache, vomiting, body pain with lower frequencies. Association of leptospirosis and urinary tract co-infection infection was found in 7.40% of cases, causative organisms isolated from the patients were pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis.