AbstractBackground:An unbalanced diet is a main risk factor for several chronic diseases. This paper identifies groups of individuals with an unbalanced diet based on the consumption of nutrients. A characterisation of the groups may help to focus efforts aimed at improving the dietary behaviour of the population.Methods:Using nutritional data of 1763 men and 2267 women participating in the German Nutrition Survey of 1998, we constructed two indices for diet quality that each combines a large amount of nutrients into a single indicator. The impact of sociodemographic and lifestyle characteristics on the diet quality indices was analysed using multiple regression analyses.Results:The results show a considerable variation of diet quality between different groups of individuals. High diet quality in terms of the consumption of vitamins, minerals and trace elements is positively associated with income, education level, age, energy intake, food diversity, sport activity and vegetarianism. On the other hand, a low diet quality as indicated by high intakes of e.g. fat, sugar, alcohol and sodium can be expected when energy intake is high, for individuals of middle age and for pregnant and breast-feeding women.Conclusion:The results of this study help to identify groups of individuals with preferable and non-preferable diet quality. For developing public health strategies, in particular the impact of age on diet quality seems to be interesting. The rising diet quality with increasing age could reflect a changing health consciousness. It could thus be a challenge for health policy to promote a healthy way of living focused especially on young individuals.