The criteria and recommended standard prepared to meet the need for preventing occupational diseases arising from exposure to methyl- parathion are presented. The proposed standard applies only to the manufacture, formulation, application, or other occupational exposure to methyl-parathion (298000) as applicable under the Occupational Safety and Health Act of 1970, intended to protect against acute systemic poisoning by methyl-parathion. Methyl- parathion is defined as 0,0-dimethyl-0-p-nitrophenyl- phosphorothioate, and occupational exposure to it is defined as employment in any area in which methyl-parathion or materials containing methyl-parathion, alone or in combination with other substances, is produced, packaged, processed, mixed, blended, handled, stored in large quantities or applied. Serious effects are produced by methyl-parathion contact with skin mucous membranes, and eyes. Available evidence indicates that the greatest danger to employees is from skin contact and absorption through the skin. Exposure is to be limited to 0.2 milligram per cubic meter of air determined as a time-weighted average exposure for up to 10 hour workday in a 40 hour week.