A microlithographic projection exposure apparatus includes a projection lens (20) that is configured for immersion operation. For this purpose an immersion liquid (34) is introduced into an immersion space (44) that is located between a last lens (L5; 54) of the projection lens (20) on the image side and a photosensitive layer (26) to be exposed. To reduce fluctuations of refractive index resulting from temperature gradients occurring within the immersion liquid (34), the projection exposure apparatus (10) includes heat transfer elements (50; 501; 502; 503; 504) with which zones of the immersion liquid (34) can be heated or cooled in a specified manner. |