PIP: The ability of a scale, called the marital instability index, to predict divorce or permanent separation in the United States is examined. It is tested using data on a national sample of about 1,663 married persons under age 55 who were interviewed originally by telephone in 1980 and reinterviewed in 1983. The results show that high scorers on the scale are nine times more likely to divorce than low scorers. The process of moving from marital instability to divorce is also analyzed. The findings indicate that the marital instability index provides the basis for a comprehensive model predicting divorce, particularly if adequate information on alternative attractions to marriage and on barriers to divorce is available.