Lipoprotein and steroid hormone levels were measured in 61 bilaterally oophorectomised women who had been treated for 3 years with implants containing either oestradiol alone or oestradiol plus testosterone. The lipoprotein levels associated with each of the two therapy regimens were compared. In addition, lipoproteins were measured in 67 untreated bilaterally oophorectomised age-matched women and compared with those of the treated women. Despite the high oestradiol levels produced by both types of implant, the only significant finding was a reduced LDL cholesterol in the oestrogen/testosterone treated group as compared with that of the untreated group.