Purpose: To define importance values assigned to attributes of biological agents (BAs) by Spanish patients with rheumatic diseases (rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis) and rheumatologists. Patients and methods: This was an observational, cross-sectional design based upon a rank-based full-profile conjoint analysis. A literature review and four focus groups were undertaken to identify attributes and levels. An orthogonal matrix, combining the selected levels of attributes, was used to define scenarios. Participants ranked eight scenarios from 1 (most preferred) to 8 (least preferred). The relative importance (RI) of attributes was calculated. Multivariate regression analysis was performed to identify the characteristics that influenced the values of RI. A total of 488 patients (male 50.9%, mean age 50.6 [standard deviation {SD} 12.06] years, rheumatoid arthritis 33.8%, ankylosing spondylitis 32.4%, psoriatic arthritis 33.8%; mean time since diagnosis 12.6 [SD 8.2] years) and 136 rheumatologists (male 50.4%, mean age 46.4 [SD 9.1] years, mean time of practice 16.7 [SD 8.8] years) participated. Results: The ideal BAs for patients and physicians, respectively, should allow pain relief and improvement of functional capacity (RI 39% and 44.7%), with low risk of adverse events (RI 24.9% and 30.5%), a long time prior to perceiving the need for a new dose (RI 16.4% and 12.4%), and self-administration at home (RI 19.7% and 12.5%), as identified through their preferences. Conclusion: Although efficacy and safety are paramount for patients and rheumatologists to make a choice regarding BAs, the need for a low frequency of administration and the administration method also play a role as preference attributes for BAs.