Background: Meningitis is an inflammatory affection of the membranes surrounding the brain and spinal cord, which occurs as either a primary disease or secondarily to disease in some other part of the body. The epidemiological trend of acute meningitis varies with time and geography. Objective: To isolate the various agents of acute meningitis in all age group patients and to know the antimicrobial susceptibility pattern of bacterial isolates. Materials and Mathods: In this prospective study, a total of 316 cerebrospinal fluid (CSF) specimens were collected from patients showing signs and symptoms of acute meningitis and processed by standard microbiological methods in a tertiary care hospital in Guwahati, Assam over a period of one year, from August 2009 to July 2010. Results: Out of 316 CSF samples, bacterial and fungal culture positivity rate was found to be 16.13%. The most common bacterial isolate was Staphylococcus aureus, 29.41%. Isolation rate of Cryptococcus neoformans was 8%. All the Gram positive isolates were 100% sensitive to linezolid and vancomycin, whereas Gram negative isolates were 92% sensitive to polymyxin B. Conclusion: This study gives an idea about the changing trend of acute meningitis along with the changing in vitro antimicrobial susceptibility pattern of the bacterial isolates, which can help the clinicians to formulate the initial empiric therapy for patients of acute meningitis.