  New multiband CCD photometry is presented for the eclipsing binary GW Gem;
the $RI$ light curves are the first ever compiled. Four new minimum timings
have been determined. Our analysis of eclipse timings observed during the past
79 years indicates a continuous period increase at a fractional rate of
+(1.2$\pm$0.1)$\times10^{-10}$, in excellent agreement with the value
$+1.1\times10^{-10}$ calculated from the Wilson-Devinney binary code. The new
light curves display an inverse O'Connell effect increasing toward longer
wavelengths. Hot and cool spot models are developed to describe these
variations but we prefer a cool spot on the secondary star. Our light-curve
synthesis reveals that GW Gem is in a semi-detached, but near-contact,
configuration. It appears to consist of a near-main-sequence primary star with
a spectral type of about A7 and an evolved early K-type secondary star that
completely fills its inner Roche lobe. Mass transfer from the secondary to the
primary component is responsible for the observed secular period change.
