Interpretations of magnetic anomalies often assume negligible remanent magnetization because detailed information about magnetic properties is rarely available. This paper attempts to assess the effects of thermal remanent magnetization (TRM) on magnetic anomalies caused by intrusives. Several three-dimensional axisymmetric and two-dimensional intrusives of different sizes are emplaced at different depths and at different times, and their thermal evolutions are calculated. On the basis of these thermal evolutions, we determine their TRM patterns, assuming reversals of the Earth's magnetic field have occurred and using typical magnetic blocking temperatures for igneous rocks. Results indicate that an intrusive with a uniform distribution of magnetic minerals acquires a layered pattern of TRM. Near-surface intrusives acquire stronger magnetization than deep-seated ones. The contribution of TRM to magnetic anomalies is quite different from the contribution of induced magnetization, especially for near-surface intrusives. Interpretations of magnetic anomalies caused by deep-seated intrusives in terms of induced magnetization are more reliable than those of the anomalies which are associated with near-surface intrusives. ¿ American Geophysical Union 1989