People with schizophrenia, a disabling mental disorder, smoke at rates three times higher than those of the general population. They also tend to develop serious medical problems due to this heavy smoking. Little is known, however, about the relationship between schizophrenia and smoking. Smoking topography, the study of cigarette-puffing behavior, may help to uncover important information about the smoking habits of people with schizophrenia, and how they differ from smokers who do not have a mental illness. To develop more effective treatment approaches for schizophrenic smokers, a better understanding of nicotine addiction in this population is needed. This study will use hand-held smoking topography devices and blood tests to measure smoking behavior and nicotine levels in people with schizophrenia. This information will be compared to similar measurements in people with no mental illness and in people with bipolar disorder, another disorder associated with high rates of heavy smoking.