Summary Background Statins lower high-sensitivity C-reactive protein (hsCRP) and cholesterol concentrations, and hypothesis generating analyses suggest that clinical outcomes improve in patients given statins who achieve hsCRP concentrations less than 2 mg/L in addition to LDL cholesterol less than 1·8 mmol/L (<70 mg/dL). However, the benefit of lowering both LDL cholesterol and hsCRP after the start of statin therapy is controversial. We prospectively tested this hypothesis. Methods In an analysis of 15 548 initially healthy men and women participating in the JUPITER trial (87% of full cohort), we prospectively assessed the effects of rosuvastatin 20 mg versus placebo on rates of non-fatal myocardial infarction, non-fatal stroke, admission for unstable angina, arterial revascularisation, or cardiovascular death (prespecified endpoints) during a maximum follow-up of 5 years (median 1·9 years), according to on-treatment concentrations of LDL cholesterol (≥1·8 mmol/L or <1·8 mmol/L) and hsCRP (≥2 mg/L or <2 mg/L). We included all events occurring after randomisation. This trial is registered with ClinicalTrials.gov , number NCT00239681. Findings Compared with placebo, participants allocated to rosuvastatin who achieved LDL cholesterol less than 1·8 mmol/L had a 55% reduction in vascular events (event rate 1·11 vs 0·51 per 100 person-years; hazard ratio HR 0·45, 95% CI 0·34–0·60, p<0·0001), and those achieving hsCRP less than 2 mg/L a 62% reduction (event rate 0·42 per 100 person-years; HR 0·38, 95% CI 0·26–0·56, p<0·0001). Although LDL cholesterol and hsCRP reductions were only weakly correlated in individual patients ( r values <0·15), we recorded a 65% reduction in vascular events in participants allocated to rosuvastatin who achieved both LDL cholesterol less than 1·8 mmol/L and hsCRP less than 2 mg/L (event rate 0·38 per 100 person-years; adjusted HR 0·35, 95% CI 0·23–0·54), versus a 33% reduction in those who achieved one or neither target (event rate 0·74 per 100 person-years; HR 0·67, 95% CI 0·52–0·87) (p across treatment groups <0·0001). In participants who achieved LDL cholesterol less than 1·8 mmol/L and hsCRP less than 1 mg/L, we noted a 79% reduction (event rate 0·24 per 100 person-years; HR 0·21, 95% CI 0·09–0·52). Achieved hsCRP concentrations were predictive of event rates irrespective of the lipid endpoint used, including the apolipoprotein B to apolipoprotein AI ratio. Interpretation For people choosing to start pharmacological prophylaxis, reduction in both LDL cholesterol and hsCRP are indicators of successful treatment with rosuvastatin. Funding AstraZeneca.