Aim. The objective of this study was to analyze the changes in depressive and extrapyramidal symptomatology during glycine augmentation of antipsychotic treatment in patients with schizophrenia. Materials and methods. Twenty-nine schizophrenic patients (ICD-10) with predominant negative symptoms in stable mental state participated in a 10-week open-label prospective study. Patients received stable doses of antipsychotic drugs for at least 3 months before glycine application. During the next 6 weeks patients received augmentation of antipsychotic treatment with glycine (up to 60 g per day). The first and last two weeks of observation were used to assess stability of mental state. Symptom severity was assessed using the Hamilton Depression Rating Scale (HDRS), the Positive and Negative Syndrome Scale (PANSS), and the Simpson-Angus Extrapyramidal Symptom Rating Scale (SAS). Results. In the studied group after 6 weeks of administration of glycine a significant improvement in depressive symptoms (reduced scores by 25.8% in HDRS, p < 0.001) and reduced scoring in mood symptoms of PANSS were observed. In SAS a reduction of extrapyramidal symptoms' severity (p < 0.05) was also noted. Two weeks after the glycine augmentation the symptom severity in the HDRS, PANSS, and SAS remained at similar levels. Conclusions. Glycine augmentation of antipsychotic treatment may reduce the severity of depressive and extrapyramidal symptoms. Glycine use was safe and well tolerated.