Infections are among the leading causes of morbidity and mortality in lymphoproliferative malignancies such as multiple myeloma (MM) and chronic lymphocytic leukemia (CLL). The causes of infections are often multifactorial and may be due to disease- or treatment-related factors. New therapies have improved survival in lymphoproliferative malignancies, resulting in an increased incidence of secondary immune deficiencies (SID) in these diseases.