Perifosine is a synthetic novel alkylphospholipid, a new class of anti-tumor agents which targets cell membranes and inhibits Akt activation. Here we show that baseline phosphorylation of Akt in MM cells is completely inhibited by Perifosine in a time- and dose-dependent fashion, without inhibiting phosphoinositide-dependent protein kinase 1 phosphorylation. Perifosine induces significant cytotoxicity in both MM cell lines and patient MM cells resistant to conventional therapeutic agents. Perifosine does not induce cytotoxicity in peripheral blood mononuclear cells. Neither exogenous IL-6 nor IGF-1 overcomes Perifosine-induced cytotoxicity. Importantly, Perifosine induces apoptosis even of MM cells adherent to bone marrow stromal cells. Perifosine triggers JNK activation, followed by caspase-8/9 and poly (ADP)-ribose polymerase cleavage. Inhibition of JNK abrogates Perifosine-induced cytotoxicity, suggesting that JNK plays an essential role in Perifosine-induced apoptosis. Interestingly, phosphorylation of ERK is increased by Perifosine; conversely, MEK inhibitor synergistically enhances Perifosine-induced cytotoxicity in MM cells. Furthermore, Perifosine augments dexamethasone, doxorubicin, melphalan, and bortezomib-induced MM cell cytotoxicity. Finally, Perifosine demonstrates significant antitumor activity in a human plasmacytoma mouse model, associated with downregulation of Akt phosphorylation in tumor cells. Taken together, our data provide the rationale for clinical trials of Perifosine to improve patient outcome in MM.