The rare and depth of penetration of two dye markers, hematoxylin and eosin, into beef muscle were compared. The effects of temperature, aging, meat texture, and type of muscle were investigated. Samples (1 cm(3)) were placed into dye markers, and then were sectioned at selected rime intervals and examined microscopically. Hematoxylin penetrated into the meat slower than eosin; depth of hematoxylin penetration decreased with decreasing temperature, firmer meat texture and aging. Penetration rare was faster at the beginning than at the end of the test period. Penetration rate and depth of oxygen into beef, lamb, and pork were investigated also. The samples (8 cm(3)) were placed in a modified atmosphere package containing 80% oxygen and 20% carbon dioxide. The samples were cut at selected time intervals up to 26 h after addition of oxygen and oxygen penetration rate and depth were measured. Oxygen penetration war deeper in beef than in pork and deeper in pork than in lamb. Oxygen penetration rate was faster initially and then slowed as time progressed.