In this paper, we present the results of the spectral analysis of photoplethysmography (PPG) signals for normals and patients with various cardiovascular disorders. Photoplethysmography is a non-invasive technique that measures relative blood volume changes in the blood vessels close to the skin. The PPG signal of 10 subjects was recorded from the earlobes. Five of the subjects were critically ill patients (2-Atrial Flutter, 3-Post Myocardial Infarction) and the remaining five were normals. The spectral analysis indicates that the contents of the PPG signal are different for normals and cardiovascular patients. We also investigated Heart Rate Variability (HRV) using the PPG signal. These results show that PPG can be used to analyze cardiovascular disorders and supplement existing methods of analyzing HRV.