Biomarkers are important for guiding the clinical and therapeutic management of all phases of rheumatoid arthritis because they can help to predict disease development in subjects at risk, improve diagnosis by closing the serological gap, provide prognostic information that is useful for making therapeutic choices and assessing treatment responses and outcomes, and allow disease activity and progression to be monitored. Various biomarkers can be used to identify subjects susceptible to the disease and those with pre-clinical rheumatoid arthritis before the onset of symptoms such as rheumatoid factor and anti-citrullinated protein antibodies. They can be correlated with a risk of developing rheumatoid arthritis and can predict more bone erosions and severe disease progression. Biomarkers such as the erythrocyte sedimentation rate and C-reactive protein levels provide information about disease activity, while predictive biomarkers allow clinicians to assess the probability of a treatment response before starting a particular therapy particularly in the era of biological drugs. This move from traditional approaches to patient stratification and targeted treatment should greatly improve patient care and reduce medical costs.