Assuming lexicographic preferences where utility is a vector, standard consumer theory is a special case. A more general model permits a treatment of quality differences among goods. The main result is that the average quality of goods consumed is higher at higher incomes, a common observation not explained in the usual approaches. It is also shown that, excepting a singular case, the average quality is higher with a fall in price of any purchased good. Copyright 1990 by The London School of Economics and Political Science.