In 1978 a total of 2410 women were delivered at The London Hospital. Of these, 387 had placental function tests carried out during their pregnancy. The tests available were urinary oestriol and serum human placental lactogen (HPL). Women whose pregnancies were complicated by diabetes, hypertension, twins or suspected intrauterine growth retardation were most likely to have placental function tests carried out. They were requested less readily in cases of heart disease, ante-partum haemorrhage, threatened abortion and pre-eclampsia. In approximately 30% of the high risk pregnancies placental function tests were not done. More careful selection would make better use of the available tests.