Since 2013 the Passive House Institute US has seen a significant increase in the design, construction, and certification of multifamily passive buildings. Many first multifamily passive buildings, from 6- to 57-unit developments, have been completed and occupied since then. Monitored performance data are now available. This presentation will report on a detailed comparison of modeled performance predicted by passive design tools and actual measured performance data of four case study projects while occupied and under operation. This session will answer these questions: How well do the currently used passive modeling tools, algorithms, and underlying modeling assumptions match the measured performance in the field? Were the anticipated energy and carbon-reduction goals met?