A method for identifying one or more genes involved in a phenotype of cells, tissues or organisms, comprising the steps of contacting cells, tissues or organisms which exhibit the phenotype with a library of antisense oligonucleotides and performing a primary phenotypic assay to determine which antisense oligonucleotides in the library attenuate the phenotype. These antisense oligonucleotides correspond to genes involved in the phenotype. The method may be used to identify genes involved in various disease states.