Materials for ESP reflect the specific language needs that are being addressed and have much in common with ”general” ESL/EFL materials, but there are important distinctions as well. Like the field of ESL/EFL in general, ESP has evolved considerably over the past 50 years, and the impact of this evolution can be seen in the area of materials development. While much has been written on ESL materials development, discussion focusing on the issues involved in the development and use of materials in ESP contexts has been less robust. This paper first provides an overview of language learning materials in general. Particular features and challenges with ESP materials are then discussed, looking specifically at the role of needs assessment and the questions about the level of specificity required in ESP materials. The paper concludes with suggestions for 'best practices' in identifying and preparing ESP materials.