This paper reports the investigation of the growth and spectroscopic properties of Er3+/Yb3+-co-doped Ca3Gd2(BO3)(4) and Ca3La2(BO3)(4) crystals. Both crystals have been grown by the Czochralski method. The specific heats are 0.37J/g/K and 0.45J/g/K at 350 K for Er3+/Yb3+ :Ca3Gd2(BO3)(4) and Er3+/Yb3+:Ca3La2(BO3)(4), respectively. They have a large absorption coefficient and broad full-width at half-maximum, which are 22cm(-1) and 7nm for Er3+/Yb3+:Ca3Gd2(BO3)(4) and 14.5cm(-1) and 9nm for Er3+/Yb3+ :Ca3La2(BO3)(4), respectively. A strong emission band at 1450-1650 nm due to the I-4(13/2)-> I-4(15/2) transitions in Er3+ was observed. The fluorescence lifetimes are about 590 and 650 ps for Er3+/Yb3+:Ca3Gd2(BO3)(4) and Er3+/Yb3+:Ca3La2(BO3)(4) crystals, respectively. The results show that when Yb3+ and Er3+ ions were co-doped into Ca3Gd2(BO3)(4) and Ca3La2(BO3)(4) crystals, Yb3+ as the sensitizer can enhance the absorption efficiency and lower the laser oscillations threshold of 1.5 mu m Er3+ laser. (c) 2006 Elsevier B.V. All rights reserved.