To characterize the pharmacokinetic profile of pegylated liposomal doxorubicin formulations, a multicenter, randomized, two-period crossover study was conducted in 74 patients with advanced ovarian cancer or metastatic breast cancer. Blood samples were collected up to 336 hours post-dose, and plasma concentrations of encapsulated and free doxorubicin were quantified using validated LC-MS/MS methods. Pharmacokinetic parameters (Cmax, AUC0-t, AUC0-inf, tmax, t1/2, Vd, and Cl) were calculated using noncompartmental analysis.