Galactomannan (GM) is a polysaccharide component of the Aspergillus cell wall released from growing hyphae. Serum galactomannan can often be detected between 7 to 14 days before other diagnostic clues become apparent. Monitoring of galactomannan levels can potentially allow initiation of presumptive antifungal therapy before life-threatening infection occurs. The test aids in the diagnosis of Invasive Aspergillosis (IA) and assesses response to therapy. Invasive Aspergillosis is reported in 5-20% of cases with prolonged neutropenia, post transplantation and in patients on immunosuppressive therapy. It has a high mortality rate of 50-80% and approximately 30% cases remain undiagnosed and untreated .