We report a 59-year-old acromegalic woman, who presented with generalized bone pain, weakness, fatigue and foamy urine, who was found to have multiple myeloma (MM); and a 60-year-old acromegalic woman with dizziness, vomiting and abdominal pain, high blood pressure and splenomegaly that was posteriorly diagnosed as having Waldenstrom's macroglobulinemia (WM). Acromegaly is an uncommon disease and epidemiological studies have provided increasingly debated evidence that elevated IGF-I levels might enhance the neoplastic risk, and that cancers constitute the third leading cause of mortality in acromegaly. It is known that GH and IGF-I can activate B cell lymphocytes, and that IGF-I receptor is universally expressed in MM cells. Although the complication of acromegaly with WM or MM in patients has rarely been reported until now, we described two case reports of acromegalic patients with those hematological neoplasias, which allow a discussion about this controversial issue.