Magnetic behavior for the three series of alloys U1−xYxCu2±ySi2∓y, U1−xYxCr2Si2, and U(Cu1−xCrx)2Si2has been studied in the temperature range from 2 to 550 K. In all cases a complete solid solution with the ThCr2Si2type of structure was observed from x‐ray powder analysis with no ordering among the substituting atom species. Whereas YCu2Si2did not reveal any homogeneous region on Si/Cu substitution, uranium‐rich alloys show significant changes in the unit cell dimensions when comparing U1−xYxCu2Si2and U1−xYxCu2+ySi2−y. In both latter alloy series a negative deviation of thecparameter from Vegard’s rule is found almost compensated for by a positive deviation ofawhen Y is substituted for U. Substitution of Cu by Cr resulted in a linear dependence of the lattice dimensions.YCu2Si2and YCr2Si2are temperature independent Pauli paramagnets above 2 K, whereas the UCu2±ySi2∓yand the U(Cu1−xCrx)2Si2systems are characterized by the onset of ferromagnetic ordering atTM=105 K. AboveTMall samples are in the paramagnetic state in which the uranium atoms carry an effective moment larger than 2 &mgr;B. Saturation moments reveal a maximum for a copper deficiency ofy∼0.1, whereas excess copper correlates with a strong magnetocrystalline anisotropy indicating the presence of narrow domain walls. Substitution of U by Y in U1−xYxCu2±ySi2∓yleads to a linear decrease ofTMand for concentrations of 0.4≤x≤0.8 metamagnetic behavior is observed. The antiferromagnetic transition is followed by a ferromagnetic alignment of the U atoms below the Ne´el temperature. The maximum of the anisotropy energy coincides with the minimum in thecparameter atx∼0.65. The Y‐rich alloys U1−xYxCu2∓ySi2±ydisplay antiferromagnetism with a rather complex structure as indicated by the change of sign of the paramagnetic Curie–Weiss temperature &thgr;p. In the U1−xYxCr2Si2alloys the antiferromagnetic coupling is destroyed by rather small amounts of Y.