This paper reviews the causes of sample disturbance and its impact on laboratory measured design parameters for soft clays. It is the most significant issue affecting the quality and reliability of laboratory test data. All key design parameters such as compressibility, yield stress and undrained shear strength are adversely influenced by sample disturbance. Each stage of the sampling process, from initiation of drilling to final preparation of laboratory test specimens, causes potential disturbance to samples and is described in the paper. Several practical solutions are presented, which if properly implemented can reduce the degree of sample disturbance. These include the use of weighted drilling mud, special tube sample geometry, fixed piston samplers, and proper sealing and handling of samples. Qualitative and quantitative methods of assessing sample quality are also presented together with examples from case studies.