Nine pigs with decreased litter size or sired by boars with decreased litter size were found to be reciprocal translocation carriers. Four Large White animals (two females and two males) demonstrated translocations involving chromosomes 1 and 9 (1p-;9p+), 11 and 13 (11q+;13q-), 3 and 13 (3;13)(p1.5;q3.1), and 15 and 17 (15;17)(q1.3;q2.1). Two Large White x Pietrain terminal boars demonstrated translocations involving chromosomes 11 and 16 (11;16)(p1.4;q1.4), and 6 and 14 (6;14)(q2.7;q2.1). The (9;15)(p2.4;q1.3) and (6;16)(q1.1;q1.1) translocations were found in a Large White x French Landrace boar, and in a commercial male line boar with decreased litter size, respectively. A Gascon breed boar with reduced prolificacy also had an abnormal karyotype, namely 38 XY, rcp(1;6)(q1.2;q2.2). Reduction in prolificacy was estimated accurately in cases 3, 5, 6, 7, and 9 (35%, 30%, 35%, 41%, and 56%, respectively). Rcp(1;6)(q1.2;q2.2) and rcp(6;16)(q1.1;q1.1) seemed to have been of de novo origin.