Treatment modiﬁcations, including dose escalations and reductions, switches, discontinuations and restarts of biological therapies, are often necessary and important in the ‘real-world’ management of moderate-to-severe psoriasis. We examined the treatment utilization patterns of adalimumab,etanercept and ustekinumab among biologics-naive and non-naive patients with psoriasis enrolled in the British Association of Dermatologists’ Biologic Interventions Register (BADBIR).We also assessed the patterns of use of conventional systemic therapies in combination with biological therapies in BADBIR. The cohort study included adults with chronic plaque psoriasis who were registered with BADBIR and followed up for at least 12 months. Treatment modiﬁcations were assessed during the ﬁrst year of therapy. The time–trend method, comparing the annual cumulative dose the patients received with the annual recommended cumulative dose per product prescribing information based on the National Institute for Health and Care Excellence guidelines, was used to assess dosing patterns.Bridging therapy was deﬁned as conventional systemic therapies co-prescribed during the induction of the biological therapy (≤ 120 days), while rescue therapy was deﬁned as additional medication required following the induction phase(> 120 days). In total, 2980 patients with a mean age of 45.9 years were included, of whom, 79.2% were biologic naive. Data for patients on adalimumab (n = 1675), etanercept (n = 996) and ustekinumab (n = 309) were available. Over 12 months, 77.4% of patients continued with the biological therapy, 2.6% restarted therapy after a break of at least 90 days, 2.5% discontinued and 17.5% switched to an alter-native biological therapy. Most patients (85.7%) received there commended cumulative dose of the biological therapy,6.2% were exposed to a lower cumulative dose and 8.1%were exposed to a higher cumulative dose. Speciﬁcally, 4.5%,11.4% and 17.7% of adalimumab, etanercept and ustekinumab patients (P < 0.01), respectively, were exposed to a higher cumulative dose. A total of 749 (25.1%) patients used conventional systemic therapies in combination with biological therapy at some stage; methotrexate was the most commonly co-prescribed therapy (n = 458; 61.2%). Of those using combination therapy, 454 (60.6%) continued the use of the conventional systemic therapy for > 120 days after the start of the biological therapy, whereas 160 (21.4%) and 152(20.3%) used the conventional systemic therapy as bridging and rescue therapy, respectively. In summary, one-ﬁfth of patients starting biological therapy in BADBIR experienced treatment modiﬁcations within the ﬁrst year. Modiﬁcations included dose escalations and reductions; restarting treatment after a break; and discontinuing or switching to an alternative biological therapy. Conventional systemic therapies, particularly methotrexate, are commonly used concurrently with bio-logical therapies; this should be considered when evaluating treatment response and adverse events.