['Injection of different size ranges and concentrations of polyvinyl alcohol (PVA) foam particles was performed to determine the optimal and maximum size ranges and concentrations that may be injected reliably through microcatheters used for vascular embolization.', 'Eight different microcatheters were tested. Six different size ranges of PVA foam particles (three each from two manufacturers) at three different concentrations were tested with each catheter. All PVA foam particles were suspended in dilute low-osmolarity contrast material. For each size range and concentration of PVA foam particles, sixty 1-mL injections were made into each catheter tested. Continuous pressure monitoring was employed during all injections.', 'For each catheter, the authors determined recommended maximum size ranges of PVA foam particles that may be injected with reasonable pressure and minimal risk of inadvertent catheter occlusion. Among the four catheters used with 0.014-0.016-inch guide wires, the authors found that PVA foam particles as large as 1,000-1,500 microm could be injected without catheter occlusion. PVA foam particles as large as 710-1,000 microm could be injected through one catheter used with 0.010-0.013-inch guide wires. Particles as small as 300-500 microm occluded the other catheter used with the same size guide wires. Both of the flow-directed microcatheters tested would allow injection of PVA foam particles as large as 355-500 microm.'] Do polyvinyl alcohol foam particle sizes and concentrations injectable through microcatheters?