This STAT3 (phospho Tyr705) Cell Based ELISA Kit allows for the detection of STAT3 (phospho Tyr705) and the effects that certain stimulation conditions have on STAT3 (phospho Tyr705) expression in different cell lines. Qualitative determination of STAT3 (phospho Tyr705) concentration is achieved by an indirect ELISA format. In essence, STAT3 (phospho Tyr705) is captured by Anti-STAT3 (phospho Tyr705) Antibodies while Dye 1-conjugated and Dye 2-conjugated secondary antibodies bind the Fc region of the primary antibody. Through this binding, the dye conjugated to the secondary antibody can emit light at a certain wavelength given proper excitation, hence allowing for a fluorometric detection method. A monoclonal antibody specific for human GAPDH is included to serve as an internal positive control in normalizing the target RFU values. Anti-STAT3 Antibody is also included for normalization purposes. The RFU values obtained for the non-phosphorylated target can be used to normalize the RFU value for the phosphorylated target.