The pore-forming subunits of potassium channels are encoded by more than 70 distinct genes. Expression of distinct genes allows potassium channels with diverse properties to be encoded several of which are implicated in the physiological control of vascular function. However, a variety of posttranscriptional mechanisms can further extend the phenotypic diversity of potassium channels including heteromeric assembly of subunits, association with accessory subunits, assembly with distinct signalling complexes and alternative pre mRNA splicing. Alternative pre mRNA spicing is particularly prevalent in single gene families as exemplified by large conductance voltage- and calcium- activated potassium (BK) channels encoded by the KCNMA1 gene. Here we discuss how dynamic control of alternative pre mRNA splicing of BK channels can dramatically modify their functional properties and regulation by divergent signalling pathways. The implications of alternative splicing for analysis of the control of the microcirculation will be discussed.