Currently, citric acid is produce through microbial fermentation using various microorganisms in three different techniques, viz. submerged culture fermentation (SmF), solid-state fermentation (SSF) and liquid surface fermentation (LSF). Majority of the present commercial production of citric acid is through submerged culture fermentation by using A. niger on by-product of sugar industry as substrate. However, lately, exploitation of solid state fermentation has demonstrated some prospective in becoming a substitute to submerged fermentation for the commercial production of citric acid. In view of finding an alternative fermentation technique for citric acid production which is more effective, fuel-efficient, labour-saving and economical than the existing ones, this review discusses a comparative account of solid-state fermentation and submerged fermentation.