Recent data on ππ andK−K production are analysed in order to explore resonant effects in isospin zeroS wave scattering near theK−K threshold. Various coupled-channel formalisms are considered and information from above and below threshold is used. We identify, and determine the properties of,S* and ɛ (1400) resonance structures. The ɛ (1400) is in agreement with the results of a recent ANL analysis. TheP matrix formalism appropriate to four quark bound states is studied and found to provide an inefficient description of the observed effects. The implications for scalar meson spectroscopy are discussed.