Protocadherins are a large family of cadherin-like cell adhesion proteins that are involved in the establishment and maintenance of neuronal connections in the brain. There are three protocadherin gene clusters, designated alpha, beta and gamma, all of which contain multiple tandemly arranged genes. PCDH18 (protocadherin 18), also known as PCDH68L, is a 1,135 amino acid single-pass type I cell membrane protein that contains six cadherin domains and a cytoplasmic tail that differs from classical cadherins. Expressed ubiquitously with highest expression in ovary and lung, PCDH18 interacts with Dab1 and functions as a potential calcium-dependent adhesion protein that may be involved in the establishment of cell-cell connections in the brain. Multiple isoforms of PCDH18 exist due to alternative splicing events.