A map of the surface reflectivity of Venus at a wavelength of 3.8 cm is obtained by using a fixed base line radar interferometer. The two-fold hemispheric ambiguity in the range-Doppler map has been resolved by interferometry. The map covers a region extending approximately from −80° to 0° longitude (Carpenter's definition) and from −50° to 40° in latitude. The map shows many new features in addition to delineating clearly features already observed. Large circular regions with a radar appearance similar to lunar maria are among the newly observed features. Analysis of the method employed in resolving the hemispheric ambiguity shows that the relatively small range of projected base line change available produces only small sidelobes in the noise level.