Although the data on hemophagocytic lymphohistiocytosis (HLH) has gradually increased, the neonatal-onset HLH patients have usually been reported as case reports or together with other age groups of patients. The aim of this study was to draw attention to the clinical and laboratory,characteristics of neonatal HLH cases. Herein, the data of 8 primary, neonatal-onset HLH patients are reported. Mutational analyses were performed in 7 of the patients and Mutations in UNC13D gene were detected in 3 of the patients, whereas 2 patients were found to have perform gene mutation. Four of the patients were symptomatic within the initial 10 days of life. One patient with perforin mutation (1122 G > A) had a very severe clinical Course and died on the seventh day of life before receiving any specific treatment. Another patient with UNC13D 2783 G > C, who became symptomatic on the sixth day of life, underwent early hematopoietic stein cell transplantation and is currently alive at 8 years of age. Two of these 4 patients had extensively high serum ferritin levels mimicking neonatal hemochromatosis. Of the 4 patients who became symptomatic after 20th day of newborn period, I was found to have perforin gene mutation (445 G > A) and 2 siblings were detected to have a missense mutation in UNCI 3D (640 C > T) gene. The latter patients with UNC13D mutations could survive 3 and 4 months, although their parents ceased therapy. The patient with perforin mutation survived I I months.