The structure, magnetostriction, and anisotropy compensation of (Tb1−xPrx)(Fe0.4Co0.6)1.9 (0 ⩽ x ⩽ 1) alloys were investigated. It was found that the matrix of (Tb1−xPrx)(Fe0.4Co0.6)1.9 alloys is a (Tb,Pr)(Fe,Co)2 phase with a MgCu2-type cubic Laves structure, and a second phase of small amount is a (Tb,Pr)(Fe,Co)3 phase when x ⩽ 0.2 and x = 0.5 and 1.0. In the range 0.2<x ⩽ 0.4, the amount of the (Tb,Pr)(Fe,Co)3 phase with a PuNi3-type structure increases with increasing x and becomes the main phase when x = 0.4. When 0.5<x ⩽ 0.6, the (Tb,Pr)(Fe,Co)3 phase increases sharply, whereas the 0.6<x ⩽ 0.8, it decreases with increasing x. The spontaneous magnetostriction λ111 of the alloys exhibits a peak near x = 0.8 (λ111 = 2370×10−6). The magnetostriction ∣λ∥−λ⊥∣ at room temperature was also examined. © 1997 American Institute of Physics.