Objective. To evaluate drug survival, effectiveness, pharmacokinetics, immunogenicity, and safety in daily practice after transitioning treatment from original reference infliximab (Remicade [REM]) to a biosimilar infliximab (CT-P13 [Remsima; Inflectra]) in patients with rheumatoid arthritis, psoriatic arthritis, or ankylosing spondylitis.Methods. Of the initial 222 REM-treated patients, 192 agreed to transition to CT-P13 and were included in this multicenter prospective cohort study. Changes in the Disease Activity Score in 28 joints using the C-reactive protein level (DAS28-CRP) and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and changes in the CRP levels, infliximab trough levels, and anti-infliximab antibody levels were assessed after 6 months, and adverse events (AEs) were documented. Drug survival and prognostic factors were analyzed using Kaplan-Meier and Cox regression analyses.Results. During 6 months follow-up, 24% of the patients (n = 47) discontinued CT-P13. Thirty-seven patients restarted REM, 7 switched to another biologic drug, and 3 continued without a biologic drug. The DAS28-CRP remained stable from baseline to month 6, with a mean AE SD score of 2.2 AE 0.9 at baseline to 2.2 AE 0.8 at 6 months (difference of 0.0 [95% confidence interval (95% CI) -0.1, 0.2]). The BASDAI increased from a mean AE SD of 3.8 AE 2.0 at baseline to 4.3 AE 2.1 at 6 months (difference of +0.5 [95% CI 0.1, 0.9]). The CRP levels, infliximab trough levels, and anti-infliximab antibody levels did not change. Just prior to CT-P13 discontinuation, the DAS28-CRP components tender joint count and patient's global assessment of disease activity, as well as the BASDAI were increased compared to baseline. The most frequently reported AEs were arthralgia, fatigue, pruritus, and myalgia. A shorter REM infusion interval (hazard ratio: 0.77 [95% CI 0.62, 0.95]) at baseline was predictive of discontinuing CT-P13.Conclusion. In our cohort, one-fourth of patients discontinued CT-P13 during 6 months of follow-up, mainly due to an increase in the subjective features of the tender joint count and the patient's global assessment of disease activity and/or subjective AEs, possibly explained by nocebo effects and/or incorrect causal attribution effects.