The effect of filling of the posterior cerebral artery (PCA) on memory performance during the intracarotid sodium amytal test (IAP) was investigated in 57 patients with unilateral temporal epileptic seizure foci under consideration for surgical therapy. Memory functioning was tested following injection of the internal carotid artery contralateral and ipsilateral to the side of seizure focus. In both cases, patients with PCA filling observed using conventional angiography showed a greater memory deficit, although this effect was more robust with contralateral injections. In a subsample of patients with left hemisphere dominance for language, the effect of PCA filling on memory performance was only significant when the right hemisphere was injected. The implications of these findings are discussed in terms of the validity of the IAP test and the different factors that need to be taken into account when interpreting IAP memory performance.