The white blood cell count and mean platelet volume determined shortly after the symptom onset are known as independent predictors for clinical outcome after stroke. In the present study we sought to evaluate the prognostic value of platelet-derived inflammatory biomarkers measured prospectively after an ischaemic event. Using five-colour flow cytometry, the platelet surface expression of CD40L, CD62P and subpopulations of leukocyte-platelet aggregates were assessed in 93 stroke patients on the first (V(0)), 10th (V(1)) and 90th (V(2)) day after stroke, and once in 65 disease controls. The clinical outcome was evaluated using the Scandinavian Stroke Scale (SSS) and modified Rankin Scale (mRS) at the same time points as blood sampling and 24 months after the event. Patients with either CD40L surface expression or the percentage of monocyte-platelet aggregates (M-plt) in the third tertile (T3) at V0 had a significantly lower score on the SSS at V(1). Patients with the percentage M-plt at V(0) higher than the median value of M-plt in controls were at increased risk of SSS < 40 at V(1) (odds ratio: 2.6; 95% confidence interval [CI]: 1.4 - 8.7; p=0.006). Patients with the percentage of M-plt in T3 at V(0) showed progressive decline in survival (hazard ratio [HR]: 1.6; 95% CI: 1.1-1.9; p=0.02) and a significantly higher number of recurrent vascular events (HR: 2.64; 95% CI: 1.3-3.2; p=0.02) when compared to the first tertile. In conclusion, increased levels of M-plt could be a predictive marker for both early outcome and long-term prognosis while increased CD40L was correlated with worse clinical outcome.