  We present new optical and {\it Chandra} observations of the field containing
the ultraluminous X-ray source NGC 1313 X-2. On an ESO 3.6 m image, the {\it
Chandra} error box embraces a $R=21.6$ point-like object and excludes a
previously proposed optical counterpart. The resulting X-ray/optical flux ratio
of NGC 1313 X-2 is $\sim 500$. The value of $f_X/f_{opt}$, the X-ray
variability history and the spectral distribution derived from a re-analysis of
the {\it ROSAT}, {\it ASCA} and {\it XMM} data indicate a luminous X-ray binary
in NGC 1313 as a likely explanation for NGC 1313 X-2. If the X-ray soft
component observed in the {\it XMM} EPIC spectrum originates from an accretion
disk, the inferred mass of the compact remnant is $\approx 100 M_\odot$, making
it an intermediate mass black hole. The derived optical luminosity ($L\approx
10^5 L_\odot$) is consistent with that of a $\approx 15-20 M_\odot$ companion.
The properties of the environment of NGC 1313 X-2 are briefly discussed.
