The relationship between last abnormal biophysical profile score, in total and by variable composition, and a spectra of abnormal perinatal outcome end points was examined in 525 fetuses. Highly significant inverse relationships between last test score and outcome were observed; relationships were linear for most end points and exponential for perinatal mortality end points. For biophysical profile scores less than or equal to 6, 25 of the 26 possible variable combinations were observed, at varying frequencies. For a biophysical profile score of 6, the positive predictive accuracy for some end points was significantly higher with either nonreactive nonstress test/fetal tone absent or nonreactive nonstress test/absent fetal breathing movement, and significantly lower with absent fetal breathing movement and decreased amniotic fluid volume. For a biophysical profile score of 4, the positive predictive accuracy for some end points was significantly higher with nonreactive nonstress test/absent fetal breathing movement/decreased amniotic fluid and was significantly lower with absent fetal movement/fetal breathing movement/fetal tone. No significant variation was observed for a biophysical profile score of 2. These data indicate that not all abnormal biophysical profile scores are equal.