The development and use of the family problem-solving diary are described. The diary is one of several indicators and measures of family problem-solving behavior. It provides a record of each person's perception of day-to-day family problems (what the problem concerns, what happened, who got involved, what those involved did, how the problem situation ended, and whether and why those involved were either happy or unhappy with the solution). The diary coding procedure allows each entry to be assessed in terms of the nature of the problem and the problem-solving process. The diary is a qualitative technique developed during a pilot study of family problem-solving behavior in two healthy families. It is currently being used in a study of family problem solving in a family with a diabetic adolescent and a family with a non-diabetic adolescent. The diary provides a reality base for families; a key factor in its success is motivating families to write in the diary on a regular basis via follow-up interviews. (TJH)