Abstract The monoclinic BiB 3O 6 (abbreviation BIBO hereafter) (space group C2 ) has been grown from stoichiometric melts in single crystals of dimensions up to 5×4×2 centimeters in optical quality. We have determined all independent nonlinear optical ( nlo) coefficients of second harmonic generation d ijk SHG for the fundamental λ 0=1079.5 nm. The complete determination of a d ijk SHG tensor in crystals of monoclinic or lower symmetry has not been published to our knowlegde yet. Linear optical investigations indicate a wide range of wavelengths for phase matchable processes. The highest d eff we found along the phase matched direction of second harmonic generation at 1079.5 nm is 3.2 pm/V. This value is larger than that of many other substances, such as KTiOPO 4 ( KTP) or β−BaB 2O 4 ( BBO), being widely used in applications.