Summary This paper is concerned with horizontal wells in shallow aquifers; information about a field test is presented and the development of appropriate conceptual and computational models is discussed. Particular attention is paid to the processes of flow from the aquifer into the horizontal well and the hydraulic conditions within the well. A combined computational model representing the aquifer and the horizontal well is developed. This methodology is used to study a horizontal well in a shallow coastal aquifer; a detailed pumping test is analysed using the combined model. The combined model is then used to predict the consequences of increasing the abstraction, lengthening the well or using the horizontal well for an extended period when there is no recharge. The results from the combined model indicate that the commonly adopted assumptions of either a uniform flux into the well or a constant head along the well are not suitable for this field problem.