The chromosomal inversion polymorphism in natural populations of D. subobscura was investigated near Zürich, Switzerland, in 1986 and 1987. These data are compared with earlier data from 1963, 1964 and 1984, collected in the same region. In all five acrocentric chromosomes, significant differences in the proportions of the dominant gene arrangements occurred; in the chromosomes A, I, O and U the standard order decreased from the sixties to the eighties, whereas the arrangements I1, O3+4, O3+4+8 and U1+2 became more frequent.