Wind tunnel tests of a laminar airfoil have been performed at the Institute of Aviation in Warsaw. The main goal of the investigation was to study the separation process development in subsonic and early transonic flow regime. The airfoil chord was 0.2m. During wind tunnel test the natural laminar-turbulent transition was applied. The Mach numbers were 0.3 and 0.7. Reynolds number were approximately equal to 1.22^.10⁶ and 2.85^.10⁶ respectively. The angle of incidence was increased up until the flow was fully separated. During the experimental research, chosen test methods such as pressure measurements and schlieren visualization were applied. Wind tunnel results were analyzed in terms of aerodynamic coefficients and flow separation type identification. The wind tunnel investigation revealed that separation phenomena at subsonic and transonic flow regime affected in a different manner on the airfoil aerodynamic performance. This was mainly because of the change of the flow pattern influencing on the separation process.