Calcium acts as a second messenger in many cell types, including lymphocytes. Resting lymphocytes maintain a low concentration of Ca²⁺. However, engagement of antigen receptors induces calcium influx from the extracellular space by several routes. A chief mechanism of Ca²⁺ entry in lymphocytes is through store-operated calcium (SOC) channels. The identification of two important molecular components of SOC channels, CRACM1 (the pore-forming subunit) and STIM1 (the sensor of stored calcium), has allowed genetic and molecular manipulation of the SOC entry pathway. In this review, we highlight advances in the understanding of Ca²⁺ signaling in lymphocytes with special emphasis on SOC entry. We also discuss outstanding questions and probable future directions of the field.