Large buildings greatly alter the microclimate in their vicinity. In particular the wind flows around their base are often accelerated, with the potential to cause uncomfortable or dangerous conditions. As a result, many cities have required that the impact of any new tall building be evaluated during its design. In order to bring more uniformity into the methods and criteria used in these assessments, an ASCE task committee on Outdoor Human Comfort was formed by the Aerodynamics Committee of the Aerospace Division. This paper provides an overview of the report and describes criteria (including thermal as well as wind force effects), assessment methods, and the use of building design features as control measures. The criteria that are proposed are based on the extensive experience of the committee members and other contributors on many projects. In selecting the format for the criteria, it has been born in mind that frequently they will be used in situations where lay persons, not versed in wind effects or statistics will need to understand the results. Therefore they have been couched in terms that have been found by experience to be readily understood by the non specialist. A relatively new development has been the inclusion of thermal effects in criteria.