Rheumatology 2017;56:46–57.In this analysis examining haematological changes after tofacitinib (TOF) treatment in patients with RA from pooled Phase 3 and LTE studies, TOF decreased mean lymphocyte counts and slightly increased mean haemoglobin (Hb) levels. The Phase 3 population included patients from six trials (n=4271) of TOF 5- or 10 mg BID, placebo or active comparator up to 24 months. The LTE population (n=4858) included patients from two studies (of up to 84 months), who had participated in Phase 1, 2 or 3 TOF studies.The primary objective was to determine changes in neutrophil and lymphocyte counts plus Hb levels. Secondary objectives were to assess incidence of anaemia, and to correlate changes in Hb with disease activity, fatigue and vitality.In Phase 3 studies, mean neutrophil and lymphocyte counts decreased, and mean Hb levels increased in all TOF groups. Hb levels and neutrophil counts stabilised in the LTE studies; lymphocyte count stabilised at approximately Month 48. Few patients experienced anaemia.Small changes in haematological parameters were seen with TOF treatment, and these stabilised over time. Changes in Hb levels were associated with reduced disease activity; although fatigue and vitality improved, they were only weakly correlated with increased Hb.