Coumarins, an important group of oxygen heterocycles, well known both naturally and synthetically, are used as additives to foods and cosmetics and optical brightening agents. 4-Hydroxycoumarin and its derivatives are known for their anticoagulant, antibacterial, antifungal, antibiotic, antitumor and anti-HIV activities. They are also used as agrochemicals and analytical reagents. Biscoumarins (3), the bridge substituted dimers of 4-hydroxycoumarin, have enormous potential as anticoagulants and antioxidants and some of them have also been found to be urease inhibitors. It may be mentioned here that 3,3'-methylenebis-4-hydroxycoumarin, commonly known as dicoumarol, occurs naturally in moldy clover. It is the hemorrhagic agent responsible for the sweet clover disease of cattle and has also been employed for the prevention and treatment of thrombosis. 3,3'-Arylmethylene-bis-4-hydroxycoumarins (3), commonly known as biscoumarins, are usually synthesized by condensing 4-hydroxycoumarin (1) with various aldehydes (aromatic, heterocyclic, and α,β-unsaturated) 2 using different catalysts and media. Some of these methods require long reaction time, use of expensive catalysts and organic solvents and tedious work up. In four recent papers, the said condensation has been reported to be performed in water by employing molecular iodine, ruthenium(III) chloride hydrate or surfactants like TBAB or DDS as catalyst. In two other papers, microwave irradiation, either in ethanolic solution or over solid silica surface or in aqueous medium using sulfamic acid as catalyst, has been reported to achieve this goal. All these seven groups of workers claimed their methods as green. The current literature shows that there has been a growing tendency to develop methodologies even by avoiding the use of any catalyst or surfactant. Recently, a convenient, eco-friendly and efficient method for synthesis of bis(3-indolyl)methanes “on water” has been developed in our laboratory. This method involves heating of the constituent components in appropriate mole ratio with water for an appropriate time. The same methodology has been applied by us for the synthesis of biscoumarins also, and, to our delight, the target compounds were obtained in very good to excellent yield. It is known that the presence of an electrolyte in the aqueous medium enhances the internal pressure of water and that in turn increases the rates of reactions involving decrease of the number of molecules. This encouraged us to study the above reaction in a solution containing the commonest and cheapest electrolyte NaCl. Thus, variation of the experimental condition by replacement of pure water with 5 M aqueous NaCl solution was rewarded with the results showing almost the same yield within a much shorter time. All these aspects are presented herein.