Olive oil, sunýower oil and palm olein were used in repeated potato fryings until the oils reached the limit of 25% of polar compounds allowed by law. Six groups of rats, over 28 days, were fed diets containing 8% of : olive oil ; olive oil from 69 fryings ; sunýower oil ; sunýower oil from 48 frying ; palm olein, and palm olein from 80 fryings. Body weight and food intake were monitored weekly, during days 21-28 faeces and urine were collected and ünally blood and carcasses were also collected and stored. No signiücant diþ erences were observed in food intake and body weight among the six groups of animals. The type of oil did not modify magnesium intake, the urinary and faecal excretion of this mineral nor its apparent absorption or retention. The consumption of oils from frying, however, induced an increase in apparent magnesium absorption due to a decrease in faecal magnesium excretion, but magnesium retention did not vary owing to the increase in urinary losses. Serum magnesium and magnesium contents and concentrations in carcasses were unaþ ected. Therefore, it was concluded that the consumption of used frying oils enhances magnesium absorption, independently from the type of oil, although magnesium retention is not aþ ected due to a an elevation of urinary excretion.