Precision medicine promises to deliver improved genetic testing and reporting for all patients, enabling individually tailored treatment plans. However, providing access to these benefits for global populations will require deeper thinking about ethnic diversity and genetic background in study designs. The current Human Reference Genome assembly (GRCh38), was derived from sequencing the DNA of more than 50 ethnically diverse individuals. As such, the reference sequence represents an admixed background of contributing populations and switches from one ethnic haplotype to another at multiple places. This reference-bias can impact genetic study results if it is not properly accounted for. Effective study design requires representation of ethnic diversity both in patient populations, and in the way genetic background is represented in testing methods. This session will explore topics covering ethnic diversity in genetic testing including: expanding diversity in the Human Reference Genome, representing diversity during the design of genetic tests, and improving carrier testing with population-specific reference sequence.