The present industrial expansion has resulted in vastly increased use of x-rays and radium in the examination of materials and manufactured products. Today these applications of roentgen and gamma rays have reached a volume exceeding that of medical radiology and the exposure of a thousand films a day is not unusual for an industrial equipment. In order to avoid a repetition of the injuries suffered by the pioneers of medical radiology, it is essential that the industrial users be thoroughly acquainted with the detrimental effects of radiation. At the same time they should have sufficient understanding of the protection problem to realize that with proper safeguards their work does not entail greater hazards than occur in other fields. These safeguards consist essentially in reducing the unwanted, or stray, radiation to a negligible amount, thereby preventing superficial injuries to the skin and hair as well as harmful systemic changes, particularly in the blood and genetic cells. On the basis of experiences gained over a period of years in medical radiology, it was estimated that a person may be exposed without danger to 0.2 r per day (or 10-5 r per second). This amount, the daily tolerance dose, does not, however, allow for the special conditions of industrial radiology or for possible genetic effects necessitating a greater margin of safety. The value of 10-5 r per second is based on a thirty-five-hour week, while today many industrial employees work fifty hours or more. Furthermore, the wider beams of radiation and higher voltages frequently used industrially increase the volume dose, that is, the total amount of radiant energy absorbed by the body. Geneticists (5) have advocated that the tolerance dose be reduced to 0.02 r per day, or less, to avoid possible damage to future generations due to the cumulative effects of radiation on the gonads. Yet that point of view is not supported by the fact that the human race has been exposed for ages to cosmic radiation, at the rate of about 0.03 r per year. This question, therefore, is by no means settled and, until more experimental and clinical evidence is available both on the genetic and the volume dose effects, it may be well to apply a factor of safety according to the voltage used, the size of field, and the type of person to be protected. Obviously, better shielding should be provided for x-ray and radium workers than for persons only infrequently exposed to radiation. This report is a summary of the writer's experiences gained from stray radiation surveys of about fifty industrial installations using voltages from 30 up to 1,000 kv. and gamma rays. The instruments used in these measurements were similar to those previously described (3, 4) and included ionization chambers with air volumes of 435 c.c. and 6,000 c.c. as well as Geiger-Müller counters.