We report a one-step and green method for the synthesis of gold nanoparticles by randomly selected 21 types of microscopic fungi. Depending on the exact type of microorganisms and experimental parameters (such as fermentation conditions) highly stable particles with various shapes and sizes were obtained from the cell -free extracts of fungi, as revealed by spectroscopic and electron microscopic measurements. The active compound in the fungal extracellular supernatants which is responsible for the bioreduction was found to be less than 3000 Da in molecular weight determined by molecular sieves. (C) 2015 Elsevier B.V. All rights reserved.