Changes of sugar concentration often affect germination, plant growth, metabolic processes and the expression of numerous genes. Plants developed effective mechanisms of perception and trans- duction of sugar signals. Glucose, sucrose, trehalose and other sugars might serve as elicitors of plant sugar signaling. Hexokinase, sucrose and glucose transporters (and specific sugar receptors) have been proposed as components of sugar sensing machinery. Roles of G-proteins and specific serine/threonine kinases and phosphatases in sugar signal transduction in plant cell are discussed. The interaction of sugar signaling pathways with other signal transduction pathways operating in plant cells is emphasized.