Although intermittent bolus antibiotic therapy is currently the standard of practice for pneumonia, β-lactams exhibit time-dependent bacterial killing. Use of a prolonged infusion has been advocated for maximizing the time above the MIC compared with intermittent bolus dosing. To examine the clinical properties of the β-lactam antibiotics and the rationale for their prolonged infusion, and to validate reasons that this mode of administration may be replaced intermittent infusion as the standard of practice in ventilator associated pneumonia (VAP). 17 patients, who were diagnosed VAP with gram negative pathogens were examined by chart review observational retrospective study in academic medical intensive care unit in Chonbuk national university hospital. Each received β-lactams by prolonged infusion over 3 hours q8h were assigned. 12 patients have changed to cefepime prolonged infusion, another 5 patient treated with ceftazidime. Negative microbial conversion identified in 4 patients (4/12, 33%). Radiologic improvement disclosed in 10 patients (10/17, 59%). Laboratory findings improved as fol-lows; white blood cell count (12/17, 71%), high sensitive C-reactive protein level (12/17, 71%), procalcitonin level (7/15, 47%). Renal impairment reported in 4 patients (5/17, 29%). Prolonged infusion β-lactam antibiotics may have value in VAP subsets of patients, such as those with highly-resistant Gram-negative infections. The safety profile were acceptable, therefore further enrollment should be scheduled.