COST 240 is a pan-European action collaborating on the investigation of techniques for modeling and measuring photonic components. This action has concentrated on inter- laboratory comparison of measurement and modeling techniques using round-robin measurement of sample devices. The present paper reviews the work performed within this action on measurement of and parameter extraction from single frequency semiconductor laser diodes. Specifically, those measurements that have been made in order to estimate laser parameters include; Relative Intensity Noise, modulation response, emission linewidth, several static characteristics and amplified spontaneous emission below threshold. Some of the parameters that can be estimated from these measurements include; threshold current, external efficiency, diode resistance, internal loss, characteristic temperature, differential gain, gain compression parameter, facet reflectivities, facet phases, index and gain coupling coefficients, and group refractive index. Following a review of the typical measurements performed on circulated lasers within the COST 240 Action by participating laboratories, a brief description will be presented of the physical models adopted to extract the laser diode parameters. Examples will be presented and conclusions given as to the suitability of certain techniques for the extraction of diode parameters for single frequency lasers.