INTRODUCTIONWe examined comorbidities, comedications and polypharmacy among people living with HIV (PLHIV) and associated challenges with HIV antiretroviral therapy (ART). METHODS A cross-sectional design was used in web-based surveys conducted during 2019 in France, Germany, Italy, and the UK. Pooled sample comprised 120 internists/ infectious disease specialists managing ≥50 HIV patients, and 1171 adult PLHIV combined who participated in two separate surveys, the Positive Perspective Survey (n=483), and the Unmet Needs Survey (n=688). The outcomes were perceptions and behaviors towards ART based on PLHIV and healthcare provider (HCP) perspectives. RESULTS According to HIV physicians, challenges associated with comedications were a major reason for their patients not starting ART, or stopping, switching, or skipping their HIV treatment after they started. In total, 16.8% of providers indicated that their patients had not started ART because of medical reasons/comorbidities that interfered with dosing (France 21.7%, Germany 15.4%, Italy 6.9%, and UK 24.1%). Other reasons cited by providers for patients not starting HIV treatment were: concerns about drug tolerability/side effects (overall 34.6%, France 39.1%, Germany 34.6%, Italy 27.6%, and UK 37.9%); concerns about long-term toxicities (overall 26.2%, France 39.1%, Germany 26.9%, Italy 24.1%, and UK 17.2%), as well as concerns about drug-drug interactions (overall 16.8%, France 13.0%, Germany 26.9%, Italy 17.2%, and UK 10.3%). Averaged across all ART regimen types, the percentage of PLHIV in the Unmet Needs Study who indicated that they needed monitoring when taking other medications with their ART was 5.8%, 15.9%, and 24.1% among those with none, 1, or ≥2 non-HIV comorbidities, respectively. Within the Positive Perspectives Survey, overall prevalence of polypharmacy was 38.8% (France 41.9%, Germany 24.2%, Italy 40.8%, and UK 48.0%). Compared to those without polypharmacy, those reporting polypharmacy had lower odds of reporting viral suppression (adjusted odds ratio, AOR=0.40) and optimal overall health (AOR=0.65); they were however more likely to be worried about taking more medicines as they grew older (AOR=2.15), and to be more concerned how their ART might affect other medicines they took (AOR=2.35) (all p<0.05). CONCLUSIONS A significant unmet need remains for PLHIV relating to co-management of comorbidities and associated challenges such as polypharmacy. Polypharmacy was associated with suboptimal self-rated health and concerns about the risk of long-term negative impacts from ART intake. Holistic care that provides simplified regimens to medically complex patients can help improve treatment outcomes.