Single crystals of the magnetic oxide YbCoGaO4 have been grown for the first time. The optical floating zone image furnace was used for this purpose. The obtained single crystal was characterized by X-ray diffraction at room temperature, and refined in the R (3) over barm space group, as observed in other members of the LnCoGaO(4) family. Magnetic susceptibility measurements show relatively complex behavior, with classic spin glass phenomena observed below 11 K. (C) 2002 Published by Elsevier Science B.V.