It is suggested that temperatures in museums be kept between 72° F and 80° F with every effort to keep to the low end of this range. The relative humidity should be chosen to allow for the greatest constancy year round - in cold climates perhaps a rather low value of 45per thousand could be chosen and in warm humid climates a value nearer 58per thousand would be more reliably maintained. The importance of controlling microclimates both in the museum and in display cases is emphasized. Suggestions for the design of good display cases are made and the importance of monitoring the museum climate is discussed. Recommendations are made for protecting museum collections during climatic emergencies.