Apoptosis, a programmed form of cell death, is an important mechanism that maintains cellular homeostasis. The cellular content of tissues is regulated by a balance between cell proliferation and cell loss. Apoptosis is important not only in physiological conditions but in pathological processes as well. Apoptosis has been implicated in the pathogenesis of certain renal diseases. In human models, systemic lupus erythematosus (SLE) and IgA nephropathy have been the main interests. These studies have mainly shown that apoptosis is important in the control of mesangial cell population. We have attempted to define the role of apoptosis in a cohort of childhood lupus nephritis. We have analyzed apoptosis by the terminal deoxynucleotidyl transferase (Tdt)-mediated dUTP-biotin nick end-labeling (TUNEL) method in eight SLE pediatric patients, two of whom had hereditary deficiencies of complement components. Although the sample size was small because of the rarity of hereditary complement deficiencies, we have shown that apoptotic activity was the greatest among these pediatric patients. It has been previously suggested that in lupus, autoimmunity develops as a result of inadequate clearance of apoptotic blebs containing nuclear elements; complement deficiencies are the most important hereditary factors predisposing to the inadequate clearance of apoptotic particles. This is the first time this hypothesis has been evaluated in the tissue samples of hereditary complement deficiency-related proliferative lupus nephritis. On the other hand, apoptosis was not different from the other mesangial proliferative glomerulopathies in the lupus nephritis samples. Further studies are needed to confirm our preliminary findings. Apoptosis has been implicated in other renal diseases as well, such as autosomal polycystic kidney disease, and in experimental models. A short review of the relevant literature is presented highlighting the role of apoptosis in the pathogenesis and prognosis of certain renal diseases.