Abstract Plasma membrane Ca 2+ ATPases (PMCAs) are critical regulators of intracellular Ca 2+ concentration ([Ca 2+] i). Specific isoforms have also been demonstrated to interact and co-localise with members of the synapse-associated protein (SAP) family in hippocampal dendritic spines. Presently, only indirect evidence of changes in PMCA protein expression during postnatal development exists, therefore we chose to examine the postnatal developmental protein expression patterns of PMCAs 1–4 and the SAP proteins SAP102 and PSD95. Using Western blotting analysis, we compared the postnatal expression in the in vivo hippocampus to the expression within in vitro organotypic hippocampal slice cultures; a valid model of the developing hippocampus.All PMCA and SAP family members studied showed a marked increase in protein expression levels throughout the postnatal time course both in vivo and in vitro. SAP102 and the ubiquitously expressed PMCAs 1 and 4 followed a similar time course of expression within the in vivo and in vitro preparations. In contrast, the neurone-specific PMCA isoforms 2 and 3 and PSD95 displayed slight differences in early postnatal development. However, and most importantly, their expression ≥14 days in vitro (DIV) was similar to that in vivo.The results of this study demonstrate that postnatal expression of all PMCAs, SAP102 and PSD95 is similar in both the in vivo hippocampus and the in vitro organotypic hippocampal slice culture. Our results support the use of organotypic hippocampal slice cultures for future investigations of the importance of PMCAs for neuronal Ca 2+ handling and SAP family member interactions.