Two cases of symptomatic neonatal hepatic arteriovenous malformation (AVM) are presented. Both were treated with percutaneous transcatheter embolization and a commercially available polyvinyl alcohol suspension. Both infants died soon after AVM embolization. The results of laboratory examination of particle-size homogeneity of this commercial suspension demonstrate marked inhomogeneity of particle size very probably contributed to the death of these patients. A protocol has been developed to help determine appropriate particle size in individual cases; this may help prevent such catastrophic results during transcatheter embolization.