This paper describes a novel eukaryotic reporter gene, secreted alkaline phosphatase (SEAP). In transient expression experiments using transfected mammalian cells, we demonstrate that SEAP yields results that are qualitatively and quantitatively similar, at both the mRNA and protein levels, to parallel results obtained using established reporter genes. However, SEAP offers significant advantages in terms of ease of assay and assay expense, and also has the potential for quantitative assay at levels as low as 0.2 pg/ml of culture medium. These attributes suggest that SEAP may have general utility in experiments which rely on the accurate measurement of reporter gene expression levels.