AIMS/BACKGROUND OF STUDY Sickle cell anaemia has been described as a hypercoagulable state. A number of coagulation abnormalities as well as abnormalities in fibrinolysis have been described in this disorder. However, whether the activation of blood coagulation and fibrinolysis is contributory to vaso-occlusive crisis is unknown and therefore the predictive value of these coagulant and fibrinolytic proteins in determining the onset of vaso-occlusive crisis has not been documented. This study therefore aims to determine the plasma concentration of some fibrinolytic proteins (D-dimer, Plaminogen, Tissue Plasminogen Activator) and coagulant proteins;(Fibrinogen and Fibrinopeptide A) in sickle cell anaemia patients in both steady state and in vaso-occlusive crisis for the purpose of determining their clinical value in assessing and/or predicting the onset of vaso-occlusive. Study Design: This is a two –arm cross-sectional descriptive study conducted on sickle cell anaemia patients in steady states (Arm 1) and in vaso-occlusive crises (Arm 2) attending the Adult and Paediatrics Haematology Out-Patient Clinics as well as the Emergency Unit of Lagos University Teaching Hospital. Materials and Methods: Eighty (80) subjects who satisfied the inclusion criteria were recruited into the study. Of these, 25 were sickle cell anaemia subjects in steady state (Arm 1), 25 in Vaso-occlusive crises (Arm 2) and the rest (30) were HbAA controls. Plasma D-dimer, plasminogen, tissue plasminogen activator, fibrinogen and fibrinopeptide A were determined on EDTA samples of all subjects using ELISA test kits. Full blood counts, Red cell indices and prothrombin time and Activated partial thromboplastin time test were also determined. 1 Result: There was no significant difference in plasma D-dimer concentration between subjects in VOC (45.92 ± 37.29ng/ml) and steady state (51.72 ± 34.12ng/ml) P = 0.589. No significant difference was also observed in the Mean D-dimer concentration between controls (37.25 ± 34.85ng/ml) and subject in VOC and steady state P = 0.425 and 0.175 respectively. Similar findings were observed for plasma plasminogen, Tissue plasminogen activator and fibrinogen. However, there was a significant difference in plasma FPA concentration between sickle cell anaemia subjects in steady state (449.67 ± 310.01ng/ml) compared with HbAA controls (163.52 ± 86.26ng/ml), P = 0.001. Also, a significant difference was observed between subjects in VOC (680.99 ± 411.37ng/ml) compared with Hb AA controls. P= 008. In addition, with established 95% confidence interval of FPA in HbSS in VOC (503.09-858.87ng/ml) the sensitivity and specificity of this assay (FPA) greater than 503ng/ml as a predictor of VOC was 68.4% and 65% respectively. The PPI and NPI were 56.5% and 76% respectively. Prothrombin time test was significantly prolonged in steady state subjects (17.74 ± 1.31s) compared with controls (16.46 ± 0.95s) P = 0.000. The prolongation of PT observed in steady state did not occur in VOC. There was no significant difference between PT in controls and VOC (16.31 ± 0.81), P = 0.591. The APPT was significantly prolonged in both steady state (47.76 ± 4.80s) and VOC subjects (52.24 ± 5.34s) compared with controls (37.75 ± 1.41s). P = 0.000 in every case. Conclusion: Fibrinolysis is not significantly increased in sickle cell anaemia either in the steady state or during VOC. Fibrinopeptide A assay appears to be of value in the assessment of VOC in sickle cell anaemia.