Let A (C) B be an extension of integral domains and Γ a commutative,additive,cancellative,torsion-free monoid with Γ ∩-Γ ={0}.Let B[Γ]be the semigroup ring of Γ over B and set Γ* =Γ\{0}.Then R =A + B[Γ*]is a subring of B[Γ].We investigate various factorization properties which are weaker than unique factorization in the domains of the form A + B[Γ*].