The report presents two parts information on reentry of farm workers into fields with plant surfaces treated with pesticides. Part A assembles and interprets all available information regarding extent and severity of the problem of chemical pesticide residues on treated plant surfaces which may constitute a hazard to the health of workers who must in the course of their work come into substantial contact with these surfaces. It also identifies significant areas in which relevant information is not available. Part B identifies and discusses a number of problems of major interest to investigators who undertake to develop sound scientific criteria upon which to base reentry interval recommendations. Design of reentry investigation is discussed and guidelines for reentry research are provided. Salient points include selection of a satisfactory experimental plot, selection of a suitable experimental group, arrangements for reliable cholinesterase monitoring, and attention to a number of other minor, but potentially confounding variables.