Fareed R, Ansari A, Seecharran D, Munroe L. 2017. Investigating the degrading properties of three different strains of fungi on commonly used pesticides in Guyana. Biofarmasi (Rumphius J Nat Prod Biochem) 15: 5-14. Bioremediation is the use of microbes to remove various contaminants from the environment. The present research work was carried out during 2014-15. Aspergillus niger, Aspergillus flavus and Penicillium spp. were employed for biodegradation of pesticides commonly used in Guyana. Initially, the fungi were screened for ligninolytic potential by observing decolorization/degradation of a synthetic dye (Remazol Brilliant blue) in PDA agar. The degradation of dyes was noted by the change in original colour of the dye and visual disappearance of colour from the fungustreated Petri plates. In addition, accumulation of the dye by the fungal mycelium was also noticed. The fungi were then tested for their tolerance to the pesticides Diuron, Malathion and Diazinon respectively. This was done on solid media using PDA agar with amoxillin to prevent bacterial growth. The pesticides were introduced to the fungi by way of disc diffusion. Discs of a known diameter were infused with the respective pesticides at different concentrations and placed at strategic points around the inoculated fungal mycelium. The extent of inhibition was measured by comparing the growth diameter in the sample verses growth in the control. The pesticide diazinon was found to have inhibited the fungi more when compared to Malathion and Diuron. Finally, the fungi were used to degrade the pesticides in a liquid culture-Peptone Broth. The pesticide Diuron was selected because the fungi thrived best in all concentrations of this pesticide. A concentration of the pesticide Diuron was place in flasks containing the peptone broth with mycelia discs of the respective fungal strain. The final concentration of the pesticide was determined by using High Performance Liquid Chromatography (HPLC). The concentration of the pesticide in each strain of fungi was decreased. Aspergillus niger was found to have the highest rate of pesticide degradation followed by Aspergillus flavus and Penicillium.