PTEN (phosphatase and tensin homolog) activity assay is offered in a non-radioactive 96-well ELISA format that directly measures PTEN activity in vitro, and that specifically measures the lipid product of PTEN. The assay has low interference, high sensitivity and requires 10× to 100× less PTEN enzyme than malachite green-based phosphatase assays. PTEN activity is altered in multiple advanced cancers and PTEN is a negative regulator of insulin signaling and insulin sensitivity in adipose tissue, offering an excellent target for therapeutic research. PTEN enzyme is also available from Echelon.