Optical and electrical properties of ternary compounds in the Ag-Ga-Te system are reported. Vibrational properties of AgGaTe2 and AgGa5Te8 single crystals were studied using Raman scattering and infrared absorption spectroscopy. Long-wavelength spectra are analysed and the symmetry of lattice modes are reported. The semiconducting character of Ag-Ga-Te compounds is confirmed by conductivity measurements.