The prevalence of medical errors in health care systems has generated immense interest in recent years. The research on adverse events in hospitalized populations has consistently revealed high rates of adverse events. Some of these adverse events result from medical errors and a majority of these errors may be preventable. These errors can occur anywhere and at anytime in health care processes. The consequences of these errors may vary from little or no harm to being ultimately fatal to the patients. It is important to recognize that a degree of error is inevitable in any human task and human fallibility in health care should be accepted. The underlying precursors for many of these human errors may primarily be attributed to latent systemic factors inherent in today's increasingly complex health care system. The focus of adverse event analyses on individual shortcomings without appropriate attention to system issues leads to ineffective solutions. The cognitive influence on medical decision-making and error generation is also significant and should not be discounted.