A novel insertion 78,ZZ or 78,ZW, ins(3;1)(q25q27;undetermined) was revealed in chicken by double color fluorescent in situ hybridization (FISH). A fragment of chromosome 1 spanning either from q13-14 to q34-35, or from q14-21 to q36-41 bands, had been translocated to chromosome 3 at a site located between q25 to q27 bands. This has resulted in the generation of an interstitial deletion in chromosome 1 and an insertional translocation in chromosome 3. Chickens with this balanced insertional translocation are asymptomatic carriers and their fertility is not affected, but embryo mortality increases. Greater than 50% occurrence of unbalanced gametes are observed. However, progeny sex ratio is not affected.