Background: Complement activation has been implicated in the pathogenesis of RA. C1q–C4 complexes are a specific parameter of classical pathway activation. Objective: we aimed to investigate plasma levels of complement parameter; C1q and activated C4 in Rheumatoid arthritis, and also to assess their association with disease activity. Methods: 50 RA patients classified into inactive RA group whose DAS 28 <2.6 (n=23/50) and active group had DAS 28 ≥ 2.6 (n =27/50) and control group (n=20). RA patients were submitted to full history taking, full clinical examination, routine laboratory investigations,assessment of disease activity. CIq antibodies and C4d antibodies were measured using Enzyme-Linked Immunosorbent Assay (ELISA) technique. Results: The median plasma levels of C1q and C4d in RA patients (9.3, 8.7 ug/ml, respectively) was statistically significant higher than the control group (2.4 and 4.8 ugEq/ml, respectively) (P=0.01, 0.001 respectively). Active RA patients had elevated levels of C1q and C4d comparing to those with inactive disease. RA patients with elevated median levels of C1q and C4d had higher statistically significant difference than those with normal levels regarding duration of morning stiffness, VAS, 28 TJC, 28 SJC, DAS28, ESR and CRP. There was a significant positive correlation between the median of C1q and C4d levels in our RA patients (r= 0.39, P = 0.004). Also these complement parameters had positive correlation with duration of morning stiffness ( r= 0.539,0.275, P = 0.001,0.05 , respectively ), VAS (r=0.461, 0.335,P=0.001,0.017), DAS-28 (r = 0.523,0.393; P=0.001), ESR ( r = 0.561,0.454; P= 0.001) and CRP ( r =0.492, 0.411; P= 0.001). Conclusion: we can conclude that the classical complement pathway activation is correlated with disease activity in RA patients, supporting this assumption C1q and C4d levels were found to be significantly correlated with disease activity parameters.