The technology of ethanol fermentation under high gravity (HG) and very high gravity (VHG) conditions has witnessed significant progress over the last three decades owing to economic and environmental benefits. Research efforts have been directed toward comprehensive development of the technology. As a result, final ethanol concentrations in excess of 15% v/v are being achieved using saccharine and starchy substrates. Moreover, during the recent past, researchers have explored the possibilities of using unconventional and cost-effective substrates as well as nitrogen supplements in HG and VHG fermentations. On the other hand, considerable emphasis has been placed on selecting industrial strains, flocculating yeasts, and construction of novel strains that exhibit both osmotolerance and high ethanol yielding capabilities under VHG conditions. And, to further increase the cost-effectiveness, priority has been given for fermentation process control aspects such as control of redox potential and dissolved CO2 profiling, process optimization and modelling and simulation strategies. HG lignocellulosic ethanol production is an emerging area for research. (C) 2018 Elsevier Ltd. All rights reserved.