we succeeded in interviewing 85% of the sample who had responded to the previous questionnaire. Data on the male–male (MM) pairs, birth years 1940 to 1974, came from a sample initially ascertained directly from registry records, which contained all twin births. The first interview (MM1) was completed largely by phone in 1993 to 1996 and obtained a 72% response rate. This was followed by a second wave of interviews (MM2), conducted in 1994 to 1998 with a follow-up response rate of 83%. Data on AC and alcohol dependence were collected at both of these waves. We used the measures of drink frequency, regular quantity, maximum quantity, and alcohol dependence from MM1 because of the larger sample size, but frequency of intoxication was only assessed at MM2 and so those data were used. The mean (SD) age of the twins was 36.3 (8.2) at the FF4 interview and 35.5 (9.1) at the MM1 interview. Note that the FT16 sample is age standardized (~age 25) and differs in this sense from the wide age range covered in the VATSPSUD sample. The VATSPSUD alcohol section began by asking about any lifetime alcohol use. In our FF4, MM1, and MM2 interviews, 8.0, 5.0, and
