The suitability of the nine-question Malmö modified Michigan Alcoholism Screening Test (Mm-MAST) was tested on 133 40-year-old men and 140 45-year-old men attending a voluntary population health screening in a typically week-end-drinking society. With a cut-off level of two 'yes' answers 29% of the middle-aged male population has been reported to give a positive result in this questionnaire. In our study alcoholics were excluded. The amount and type of alcohol consumed per week was asked. The subjects were divided into three groups: (1) social drinkers (0 or 1 'yes' answer), (2) suspect abusers (two 'yes' answers), and (3) abusers (three or more 'yes' answers or drinking at least 280 g absolute alcohol per week). Group 2 reported drinking more than group 1, but according to biological markers they belonged better to group 1 than group 3. With the originally recommended cut-off level of two 'yes' answers 50.8% of 40-year-old men and 36.5% of 45-year-old men in our study proved positive. With the three 'yes' answer criterion the corresponding percentages were 28.5 and 24.0. Forty- and 45-year-old men in group 2 gave many positive answers in the question concerning week-end drinking and avoidance of alcohol for a time, as did 40-year-old men in the question concerning bad conscience after drinking. Beer and spirits were the most popular beverage combination and week-end drinking was the commonest drinking habit. The number of positive answers correlated well with the announced amount of alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)