Genome-wide association studies (GWAS) have made clear that single-nucleotide variants (SNVs) that occur at multiple locations across the genome can be associated with a specific condition or trait, also known as a phenotype. Phenome-wide association studies (PheWAS) invert the idea of a GWAS by searching for phenotypes associated with specific SNVs across the range of thousands of human phenotypes, or the “phenome” (Figure). Analogous to GWAS, PheWAS have shown that specific genetic variations may be associated with multiple conditions and traits.