This study investigated the effects of two medicinal mushroom extract blends, Agarikon.1 and Agarikon Plus, on two human tumor cell lines, H460 and Caco-2. The extracts were found to inhibit the growth of both cell lines in a concentration-dependent manner and induce cell cycle perturbations by delaying progression through the G1 and S phases. While a modest induction of early and late apoptosis was observed, no caspase-3 cleavage was detected. The results indicate that the extracts have antiproliferative and mainly cytostatic activity on the tumor cell lines through cell cycle disturbances and increases in p53 and p21 protein expression.