Two-solution bone cement consists of methyl methacrylate monomer and poly(methyl methacrylate) polymer dissolved together to yield a viscous solution. Two solutions are used such that the initiator, benzoyl peroxide (BPO), is placed in one solution and the activator, N,N, dimethyl-para-toluidine, is placed in the other. This approach to bone cement provides for a simplified use during surgery and eliminates some of the sources of porosity formation. However, the BPO-containing solution cement will spontaneously polymerize over time and will limit the useful shelf life of this component of the system. The activator-containing component is much more stable and is not as susceptible to spontaneous polymerization. In making two-solution cements, it is envisioned that antibiotics may be incorporated and that the polymer may be sterilized using gamma(gamma)-irradiation. Therefore, this study investigated the shelf life of the initiator-containing solution bone cement and studied the effects of initiator concentration, gamma-irradiation, gentamicin addition, and the role of storage temperature. Isothermal differential scanning calorimetry (Iso-DSC) techniques were used to monitor the polymerization of BPO-containing solutions. It was found that the shelf life was highly temperature dependent and followed an Arrhenius expression where refrigeration storage (4degreesC) yielded approximately a 12-month storage time, while 70degreesC storage results in setting in about 5-7 min. gamma-irradiation and gentamicin addition did not significantly affect the shelf life. Initiator concentration affected storage time with higher levels resulting in shorter shelf life. (C) 2004 Elsevier Ltd. All rights reserved.