Abstract
Methods for the determination of star formation rates (SFR) from integrated populations are reviewed. We discuss the assumptions and underlying uncertainties (e.g. IMF slope, M_up, metallicity, SF history etc.) used in the calibrations of UV, FIR, Halpha, and [OII] indicators. The ``universality'' of empirically calibrated indicators such as [OII] is examined. We also present preliminary results from a theoretical study with the aim to understand the systematics of forbidden line indicators and to provide new SFR indicators including optical to far-IR lines.