A genetic sexing strain of Ceratitis capitata, carrying a null mutation for ADH activity linked to the Y chromosome, was analysed cytogenetically. In addition to an insertion of a large part of the Y chromosome into chromosome 2, this strain carries two other chromosomal rearrangements, a deletion in the second chromosome and a reciprocal translocation involving chromosomes 2 and 4. The progeny of the T(2;4) translocation heterozygote with unbalanced chromosome constitution can survive up to the larval and (or) to the adult stage. These cytological characteristics are discussed in relation to the genetic sexing behaviour of this line.Key words: Ceratitis capitata, polytene chromosomes, genetic sexing.