Frequency changes in amylase allozymes and patterns of tissue-specific expression of amylase have been monitored in laboratory populations of Drosophila pseudoobscura maintained on media in which the only carbohydrate source was maltose or starch. Nonrandom changes occurred in patterns of expression, whereas no patterns in allozyme frequency changes were discernible. The nature of the pattern changes was similar to an identical study done on populations derived from a natural population several hundred miles from the population used in the present experiments. However, in the previous study nonrandom changes in allozyme frequencies were also noted. Evidently, selection on the Drosophila amylase system differs depending upon the genetic background of the population. Furthermore, the evolutionary dynamics of structural gene variants and those regions controlling its expression may be independent, a result consistent with DNA sequence data.