Contamination is the release onto Earth or another world of non-indigenous organisms or organic matter which could (a) have catastrophic consequences for any native life or (b) compromise the scientific findings of biological experiments. The urgent need to address the issues of both back-contamination and forward-contamination at the dawn of the space age was first pointed out forcibly by Joshua Lederberg in 1957. Following his advice, the National Academy of Sciences urged the International Council of Scientific Unions (ICSU) to evaluate the problem, which it did through the Committee on Contamination by Extraterrestrial Exploration and the Committee on the Exploration of Extraterrestrial Space. The National Academy of Sciences pursued its own investigation of the contamination issue through its EASTEX and WESTEX panels. More recently, with the imminent prospect of multiple sample-return probes and the suggestion that there might be life in the outer solar system new recommendations have been made by a Task Force of the National Research Council on how to handle extraterrestrial material.