  The abundance of chlorine is determined from X-ray spectra obtained with the
RESIK instrument on {\em CORONAS-F} during solar flares between 2002 and 2003.
Using weak lines of He-like Cl, \ion{Cl}{16}, between 4.44 and 4.50 \AA, and
with temperatures and emission measures from {\em GOES} on an isothermal
assumption, we obtained $A({\rm Cl}) = 5.75 \pm 0.26$ on a scale $A({\rm H}) =
12$. The uncertainty reflects an approximately factor 2 scatter in measured
line fluxes. Nevertheless our value represents what is probably the best solar
determination yet obtained. It is higher by factors of 1.8 and 2.7 than Cl
abundance estimates from an infrared sunspot spectrum and nearby \ion{H}{2}
regions. The constancy of the RESIK abundance values over a large range of
flares ({\em GOES} class from below C1 to X1) argues for any fractionation that
may be present in the low solar atmosphere to be independent of the degree of
solar activity.
