Abstract Equiatomic, face-centered-cubic, high- and medium-entropy alloys were arc melted, hot-rolled to produce recrystallized sheets, and tensile tested. The alloys having the compositions CrMnFeCoNi and CrFeCoNi exhibited a strong temperature-dependent decrease in strength with increasing temperature from −196 °C to 1000 °C, and a relatively weak strain-rate dependence (at 10 −3 and 10 −1 s −1 ). Ductility did not vary inversely with yield strength; rather, when strength doubled as the test temperature was decreased from room temperature to −196 °C, elongation to fracture increased by a factor of 1.5 to >60%. A high degree of work hardening, possibly due to deformation-induced nanotwinning, postpones the onset of necking and may be the reason for the ductility increase.