Growth of density inhomogeneities in Newtonian cosmological models with variable Λ

We analyze the growth of density perturbations in Newtonian cosmological models with continuous matter creation and obtain the time evolution equation for the mass density contrast. The special case where matter is created by the decay of a cosmological term (Λ) varying as Λ=3β${\mathit{H}}^2$ is examined. Constraints on the value of β from the observed high isotropy of the cosmic microwave background radiation are also obtained.