Object: Schizophrenia affects 1% of the population and the clinical course is highly variable. In this study, we aimed to compare the clinical characteristics of patients with schizophrenia longer than 10 years and longer than 15 years in order to contribute to the identification of the clinical appearance of schizophrenia in the prolonged disease process. Methods: 71 patients who were diagnosed with schizophrenia for a short period of 10 years and 53 patients who were followed for a period of 15 years were included. All of the patients were assessed by the Positive and Negative Syndrome Scale (PANSS), the Calgary Schizophrenia Depression Scale (CSDS), the Quality of Life Enjoyment and Satisfaction Questionnaire (Q-LES-Q), the Extrapyramidal Symptom Rating Scale The UKU (UgvalgforKliniskeUndersgelser) Side Effect Rating Scale, the Schedule for Assessing the Three Components of Insight and the Morisky Treatment Compliance Scale (MCQS) were administered. Results: The scores of PANSS Negative symptoms subscale, CBSS, BPRS and MTUS scores were statistically significantly higher in the patient group with a disease duration of 15 years or more than in the group with a disease duration of 10 years or less. When the neurological subscale scores of the UKU side effect assessment scale were compared between the two groups; they were statistically significantly higher in the patient group with a disease duration of 15 years or longer. Conclusion: As a result of this study, it has been shown that, in patients with schizophrenia, the longer the illness is, the more negative and depressive symptoms increase, as well as the insight into the patient's illness and the increased drug compliance. It is seen that there is a need for larger scale, prospective planned studies for schizophrenic patients with prolonged disease duration, to understand what is going on schizophrenia and for factors to be taken into account in such cases.