Protein Kinase C (PKC) iota/lambda is an atypical member of the PKC family of serine/threonine protein kinases. Human PKC iota is 596 amino acids (aa) in length with a predicted molecular mass of 68 kDa. The rodent ortholog, PKC lambda, shares 98% aa identity to human PKC iota. PKC iota is highly expressed in the brain and lung and is expressed at low levels in many other tissues including pancreatic islets. As an atypical PKC isoform, PKC iota/lambda is calcium-independent and does not require phosphatidylserine, diacylglycerol (DAG), or exogenous phorbol esters for activation. PKC iota/lambda is the catalytic component of the Par3/Par6/atypical PKC complex, a key regulator of the formation and maintenance of epithelial cell polarity, adherens junctions, and tight junctions. PKC iota is also oncogenic and is used as a prognostic marker in multiple cancer types.