The analytical design of vertical drains in soft clay requires knowledge of the coefficient of consolidation and also of the disturbance effects induced during the installation of the drains. Several analytical models describing the disturbance effects in different ways are proposed in the literature. The earliest and simplest models describe the disturbance effect in terms of concentric cylinders around a drain where a reduced and constant permeability is assumed, while more recent models attempt to describe the disturbance more realistically via more complex mathematical formulations. Although these new models describe the real in situ behaviour more realistically than the early ones, they may not always be suitable for practical use as many of the required variables are difficult to assess by standard investigation methods. This study investigates and discusses the difference between some of the available models and evaluates the influences on the results of the variables incorporated in the models.