Compaction of chromosome regions translocated to the pericentric heterochromatin and the break frequency in intercalary heterochromatin (IH) regions as affected by position effect modifiers (low temperature, removing the Y chromosome, genetic enhancers and suppressors) were studied. It has been shown that the factors enhancing compaction also increase the break frequency in IH regions. Data obtained are discussed from the point of view of proteins affecting the compaction of intercalary and pericentric heterochromatin regions translocated to heterochromatin under position effect.