Flow cytometric immunophenotyping of peripheral blood lymphocyte subsets is a powerful tool for evaluating cellular immunity and monitoring immune-mediated diseases. The numbers and proportions of blood lymphocyte subsets are influenced by factors such as gender, age, ethnicity, and lifestyle. This study aimed to establish reference ranges for peripheral blood lymphocyte subsets in a healthy Korean population. Blood samples from 294 healthy adults were collected. Lymphocyte subsets were analyzed using a single-platform method with a flow cytometer; white blood cells and lymphocytes were analyzed using an automated hematology analyzer. The mean value of the white blood cell count was $5,665cells/{mu}l$, and the mean values of the subtype counts (percentages) were as follows: lymphocytes, $1,928cells/{mu}l$ (35.08%); $CD3^+$ cells, $1,305cells/{mu}l$ (67.53%); $CD3^+CD4^+$ cells, $787cells/{mu}l$ (40.55%); $CD3^+CD8^+$ cells, $479cells/{mu}l$ (25.23%); $CD3^-CD19^+$ cells, $203cells/{mu}l$ (10.43%); and $CD3^-CD56^+$ cells, $300cells/{mu}l$ (15.63%). Additionally, the $CD4^+/CD8^+$ ratio was 1.81. In this study, gender and age significantly influenced blood lymphocyte subsets. Our results demonstrate that, as with other populations, a healthy Korean population has its own, region-specific, lymphocyte subset reference ranges.