ÖzBackground and Design: Homocysteine, a sulfur-containing amino acid, is known to be related with autoimmunity-inflammation, cardiovascular disease and DNA methylation. In this case-control study, we aimed to determine plasma homocysteine, folic acid, vitamin B12 and vitamin B6 levels in patients with psoriasis. Materials and Methods: Smoking, alcohol and coffee consumption habits were recorded in adult patients with plaque-type psoriasis and age-and sex-matched controls. Height and weight measurements were performed and Psoriasis Area and Severity Index (PASI) scores were calculated. Fasting venous blood samples were collected to determine homocysteine, folic acid, vitamin B12, vitamin B6, glucose, total cholesterol, triglyceride, high density lipoprotein (HDL), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) levels. Results: There was no significant difference between psoriasis patients (n=43) and controls (n=47) in body mass index and alcohol and coffee consumption. Smoking rate was significantly high in psoriasis patients. The median PASI score was 10.0 (8.3-12.8). Plasma homocysteine, folic acid, vitamin B12, vitamin B6, total cholesterol, triglyseride, ESR and CRP values were not significantly different between patients and the controls. HDL level was low in psoriasis patients (p=0.001). Plasma homocysteine level was higher in males than in females. There was no relationship of homocysteine levels with patient's age, PASI scores, ESR, CRP values and lipids. Homocysteine levels were inversely related with folic acid and vitamin B12 (p=0.000, r=-0.436, p=0.047, r=-0.204, respectively). We did not find any relationship between homocysteine and vitamin B6 levels. Conclusion: There was no increase in plasma homocysteine levels in psoriasis patients we followed up. Homocysteine level increases in inflammatory disorders and this increase is accepted as a cardiovascular disease marker. Homocysteine homeostasis may be balanced in our patients because of the genetic background and/or nutritional habits in this population Keywords: Psoriasis, homocysteine, folic acid Amaç: Homosistein kardiyovasküler hastalık, otoimmünite-enflamasyon ve DNA metilasyonu ile ilişkilendirilen sülfür içeren bir aminoasittir. Bu olgu-kontrol çalışmasında psoriazisli hastalarda plazma homosistein düzeylerinin ve homosisteini etkileyen folik asit, vitamin B6 ve vitamin B12 düzeylerinin belirlenmesi amaçlanmıştır. Gereç ve Yöntem: Polikliniğimizde takip edilen erişkin plak tip psoriazis hastaları ile yaş ve cinsiyet uyumlu kontrol grubunda alkol, kahve ve sigara tüketimi sorgulandı, katılımcıların boy ve ağırlıkları ölçüldü. Hastaların Psoriazis Alan Şiddet İndeksleri (PAŞİ) hesaplandı. Sabah açlık kan örnekleri alınarak homosistein, folik asit, vitamin B12, vitamin B6, kan şekeri, serum total kolesterol, trigliserid, yüksek yoğunluklu lipoproteinler (HDL), eritrosit sedimantasyon hızı (ESH) ve C-reaktif protein (CRP) değerleri çalışıldı. Bulgular: Psoriazisli hasta (n=43) ve kontrol grubu (n=47) arasında vücut kitle inde...