This paper reports on the use of a multimode extrinsic fibre Fabry-Perot interferometric sensor for quasi-static and dynamic fatigue loading experiments. A surface mounted extensometer was also used to measure the strain in the composite as a function of applied load. Excellent correlation was obtained between the strain data from the extensometer and the embedded EFPI sensor. With reference to dynamic loading, the sensor was found function reliably up to 1,600,000 cycles when the fatigue test was terminated. The fatigue tests were carried out using a peak stress of 260 MPa with a stress ratio of -0.40, and a frequency of 5 Hz. The signal processing technique was based on a channelled spectrum CCD spectrometer. The sensitivity of quasi-static strain measurements was approximately 30 micro-strain with a strain range of approximately -1% to 1%. The feasibility of using the EFPI sensor for stiffuiess-decay measurements during fatigue testing of composites was demonstrated. Preliminary results form the use of a single-mode EFPI sensor design for strain measurements in composites is also presented.