A dual-beam thermal lens technique has been used to obtain the absorption spectrum of the (Delta nu = 6) C-H stretch of liquid methane and methane in liquid argon solutions. The lowest concentration detected was 1 x 10(-3) (mole fraction) of CH4 in liquid Ar with a continuous wave laser power of 20 mW. The thermal lens signal is linear with the mole fraction of methane up to 1 X 10(-2) but not for higher concentrations. Considering the system CH4-Ar as an ideal solution, the factors that contribute to the thermal lens signal were calculated as a function of the concentration of methane. A mechanism of energy transfer based on the gas-phase results could explain qualitatively the dependence of the magnitude of the signal on the mole fraction of methane.