AIMS: Alcohol problems (AP) contribute substantially to the global disease burden. Twin and family studies suggest that AP are genetically influenced, though few studies have identified variants or genes that are robustly associated with risk. This study identifies genetic and genomic influences on AP during young adulthood, which is often when drinking habits are established. DESIGN: We conducted a genome-wide association study of AP. We further conducted gene-based tests, gene ontology analyses, and functional genomic enrichment analyses to assess genomic factors beyond single variants that are relevant to AP. SETTING: The Avon Longitudinal Study of Parents and Children, a large population-based study of a UK birth cohort. PARTICIPANTS: Genetic and phenotypic data were available for 4304 participants. MEASUREMENTS: The AP phenotype was a factor score derived from items from the Alcohol Use Disorders Identification Test, symptoms of DSM-IV alcohol dependence, and three additional problem-related items. FINDINGS: One variant met genome-wide significance criteria. Four out of 22,880 genes subjected to gene-based analyses survived a stringent significance threshold (q < .05); none of these have been previously implicated in alcohol-related phenotypes. Several biologically plausible gene ontologies were statistically over-represented among implicated SNPs. SNPs on the Illumina 550 K SNP chip accounted for ~5% of the phenotypic variance in AP. CONCLUSIONS: Genetic and genomic factors appear to play a role in alcohol problems in young adults. Genes involved in nervous system-related processes, such as signal transduction and neurogenesis, potentially contribute to liability to alcohol problems, as do genes expressed in non-brain tissues. This article is protected by copyright. All rights reserved.