This paper presents a genetic algorithm for the interrogation of optical fibre Bragg grating strain sensors. The method encodes the axial strain distribution along the Bragg grating, here represented through the local period distribution, into a gene. To facilitate rapid calculation of the grating reflected intensity spectrum, the transfer-matrix approach is applied. The genetic algorithm inversion method presented requires only intensity information from the sensor and reconstructs non-linear and discontinuous distributions well, including regions with significant gradients. The development of this algorithm will permit the use of Bragg grating sensors for structural damage identification, allowing them to be located in regions where strong strain non-uniformities occur.