Cisplatin treatment efficacy of malignant pleural mesothelioma (MPM) is aggravated by resistance and adverse effects. In P31 MPM cells, cisplatin induces morphological changes and apoptosis. To determine if very early (10 minutes) morphological responses corresponded to apoptosis-induction, cisplatin effects on P31 morphology were examined with phase-contrast microscopy (PCM), scanning electron microscopy (SEM), and flow cytometry (fluorescence-activated cell sorting [FACS]), and compared to apoptosis-induction over time. Increased membrane protrusions were identified with PCM and SEM, but these were not consistent with the induction of apoptosis. The authors concluded that very early morphological changes can be determined with PCM in MPM, but they did not convincingly correspond to apoptosis induction.