  We report observations of the z = 3.87 broad absorption line quasar APM
08279+5255 (Irwin et al. 1998) with the Adaptive Optics Bonnette (AOB) of the
Canada-France-Hawaii Telescope. The object is found to be a double source. The
separation of the two images is 0.35" +/- 0.02" and the intensity ratio
I_{north}/I_{south} = 1.21 +/- 0.25 in the H-band. No other image is detected
down to H(5sigma) = 21.3 within 10" from the double image. Strong support for
the lensing hypothesis comes from the uniformity of the quasar spectrum as a
function of spatial position in the image obtained with the integral field
spectrograph OASIS at CFHT. From the 2D-spectroscopy, narrow-band images are
reconstructed over the wavelength range 5600-6200A to search for emission-line
objects in a field of 15"x12" around the quasar. We find no such object to a
limit of 6x10^{-17} erg cm^{-2} s^{-1}. We use the images centered on the
deepest absorption lines of the Ly-alpha forest to dim the quasar and to
increase the sensitivity closer to the line of sight. One of the images,
centered at 5766.4A, exhibits a 3sigma excess 1.5" from the quasar to the
north-east.
