Background: Methylmalonic acidemia (MMA) and propionic acidemias (PA) are the most common organic acidemias affecting the propionate pathway. Anemia, leukopenia and thrombocytopenia due to bone marrow supression are common findings in both disorders, specially in acute metabolic decompensation. It is suggested neurological injury in each disorder and renal dysfunction in MMA is related to mitochondrial dysfunction due to toxicity of methylmalonic acid, propionyl-CoA and 2-methylcitrate, but the pathogenesis of bone marrow supression is unknown. Objectives: To evaluate whether there is any relation between blood hemoglobin, white blood cell (WBC), thrombocyte levels and urine organic acid excretions, blood free carnitin, acylcarnitine levels. Material and Methods: The study group consisted of 37 children (MMA=30, PA=7). Blood and urine samples were obtained at the same time.