Close cellular proximity and correct anatomical arrangement within islets are essential for normal patterns of insulin secretion. Thus, segregation of islets into single cells is associated with a dramatic decline in stimulus secretion-coupling and glucose-induced insulin release. Generation of pseudoislets from clonal islet cell lines provides a useful model to examine islet cell interactions and insulin secretion. Such studies have highlighted the functional importance of cell adhesion molecules and connexins. Pseudoislets comprising insulin-secreting cell lines have been shown to closely mimic primary islets in both size and morphology, displaying a significantly enhanced response to glucose, nutrients and drugs over equivalent monolayer cultures. Here, we consider the influence of islet structure and cellular interactions in the control of insulin secretion. The functional characteristics of pseudoislets derived from clonal beta-cell lines or a combination of alpha-, beta- and delta-cell lines are discussed in light of normal islet function and possible therapeutic application.