Radio-seeing effects on centimeter- and millimeter-wavelength interferometers are now reasonably well known. On the other hand, radio seeing also shows up on filled-aperture telescopes as an anomalous refraction, i.e., an apparent displacement of a radio source from its true position. The magnitude of this effect, as a fraction of the beam width, is bigger on larger telescopes, and thus its impact on the pointing is likely to become critically important in the next generation of electrically large filled-aperture radio telescopes (D/λ≳3-5¿104, where D is the diameter). Also, because of the increasing number of focal plane arrays being used for both spectroscopic and continuum astronomical observations, it is of great interest to study the atmospherically distorted shape of the telescopic point spread function and the resulting cross talk among adjacent pixels. Here we present a model study of anomalous refraction effects by producing simulations of a two-dimensional phase screen located in the aperture plane of the antenna, using the Large Millimeter Telescope as a benchmark. Then we discuss the basic concept and simulate the operation of a tip-tilt compensation method at millimeter wavelengths that would use an aperture plane array of 183 GHz radiometers. ¿ 2000 American Geophysical Union<