We present a summary of the concept design report of a new astronomical instrument: SPARC4, Simultaneous
Polarimeter and Rapid Camera in 4 bands. SPARC4 will provide photometry and polarimetry in four optical
broad bands (griz SDSS) simultaneously. This is achieved by the use of dichroic beam splitters. The square eld
of view is around 5.6 arcmin on a side. SPARC4 time resolution is sub-second for photometry and somewhat
longer for polarimetry. This is provided by the use of fast EMCCDs. The main motivation for building SPARC4
is to explore astrophysical objects which exhibit fast temporal variability in
ux and polarization. The instrument
will be installed at the 1.6-m telescope of the Observatorio do Pico dos Dias (Brazil).