  The star formation rate (SFR) is a fundamental property of galaxies and it is
crucial to understand the build-up of their stellar content, their chemical
evolution, and energetic feedback. The SFR of galaxies is typically obtained by
observing the emission by young stellar populations directly in the
ultraviolet, the optical nebular line emission from gas ionized by newly-formed
massive stars, the reprocessed emission by dust in the infrared range, or by
combining observations at different wavelengths and fitting the full spectral
energy distributions of galaxies. In this brief review we describe the
assumptions, advantages and limitations of different SFR indicators, and we
discuss the most promising SFR indicators for high-redshift studies.
