The information in this Handbook is intended to assist users of the Spacelab (SL) scientific platform on the Space Transportation System (STS). It will assist experimenters to incorporate into their experimental design and procedures features that will minimize the impact of contamination on the performance of their own and other experiments. The contamination information is presented in sufficient detail for use by most experiments. Extensive references, bibliographies, and contacts are provided for use by those experimenters who need more detailed information. The term contamination, as used in this Handbook, refers to both molecular and particulate matter, either deposited on or within the field-of-view (FOV) of a surface and at a level sensible by the instrument or surface. Contamination during all phases of hardware life is addressed. These phases are preintegration (design, manufacture, assembly, test and shipment to the STS launch site), integration (STS launch site activities prior to launch), ascent (the period from STS engine ignition to payload bay (PLB) door opening), orbit (the period during which the PLB doors are open), descent (from PLB door closure to landing site touchdown), postlanding (ground operations prior to PLB opening, including ferry flight), and de-integration (removal from the PLB and post-flight checkout). Measured and anticipated contamination levels, contamination models, contamination effects and protection methods are presented. The available data for facilities at both Kennedy Space Center (KSC) and Vandenberg Air Force Base (VAFB) are presented. This material will be updated as additional data is obtained. In addition to contamination, the effects of the space environments at STS altitudes on spacecraft materials are included in the Handbook. The environments included are atmosphere-induced mass loss (most likely due to atomic oxygen), glow of spacecraft surfaces, other atmospheric influences (density, species, temperature, drag), plasma, electromagnetic and particulate radiation, and magnetic and electric fields.