Autism is a heterogeneous neurodevelopmental disorder characterized by impairments in social interaction, language, and restricted/repetitive behaviors. Recent advances in autism genetics have identified several susceptibility genes and highlighted the role of de novo and inherited copy number variations (CNVs). Systematic approaches, including array-based expression profiling, are helping to uncover the genetic and phenotypic heterogeneity underlying autism spectrum disorders (ASDs). ASDs encompass various conditions, with autism disorder being the most severe. Boys are at higher risk, and the disorder is associated with a broad range of genetic and environmental factors. Genetic studies have shown that ASDs have a strong heritable component, with mutations in specific genes and CNVs contributing to approximately 10–20% of cases. However, no single cause accounts for more than 1–2% of cases, similar to mental retardation. Despite this heterogeneity, biological themes such as synaptic dysfunction and abnormal brain connectivity are emerging as potential mechanisms linking rare and common variants. Multiple approaches, including whole-genome and pathway-based association studies, dense resequencing, and large patient cohorts, are being used to identify genetic risk factors. Key genetic findings include mutations in genes such as NLGN3, SHANK3, NRXN1, and CNTNAP2, which are associated with synaptic function and ASD risk. CNVs, particularly in regions like 15q11–15q13, are also implicated. These studies have identified numerous candidate loci, with some CNVs contributing to a significant proportion of ASD cases. The role of rare variants in ASDs is increasingly recognized, and their interaction with common variants is an important area of research. Linkage studies have identified several risk loci, including 17q11–17q21 and 7q, but genome-wide significant results are rare. Association studies have also identified common variants, such as those in CNTNAP2, associated with ASD risk. However, the contribution of common variants remains limited, and rare mutations are more likely to be involved in ASD pathogenesis. Overall, the genetic basis of ASDs is complex, involving both rare and common variants. Understanding the interaction between these variants and environmental factors is crucial for developing effective interventions. Future research will focus on identifying the specific molecular mechanisms underlying ASDs and improving the accuracy of genetic risk assessments.Autism is a heterogeneous neurodevelopmental disorder characterized by impairments in social interaction, language, and restricted/repetitive behaviors. Recent advances in autism genetics have identified several susceptibility genes and highlighted the role of de novo and inherited copy number variations (CNVs). Systematic approaches, including array-based expression profiling, are helping to uncover the genetic and phenotypic heterogeneity underlying autism spectrum disorders (ASDs). ASDs encompass various conditions, with autism disorder being the most severe. Boys are at higher risk, and the disorder is associated with a broad range of genetic and environmental factors. Genetic studies have shown that ASDs have a strong heritable component, with mutations in specific genes and CNVs contributing to approximately 10–20% of cases. However, no single cause accounts for more than 1–2% of cases, similar to mental retardation. Despite this heterogeneity, biological themes such as synaptic dysfunction and abnormal brain connectivity are emerging as potential mechanisms linking rare and common variants. Multiple approaches, including whole-genome and pathway-based association studies, dense resequencing, and large patient cohorts, are being used to identify genetic risk factors. Key genetic findings include mutations in genes such as NLGN3, SHANK3, NRXN1, and CNTNAP2, which are associated with synaptic function and ASD risk. CNVs, particularly in regions like 15q11–15q13, are also implicated. These studies have identified numerous candidate loci, with some CNVs contributing to a significant proportion of ASD cases. The role of rare variants in ASDs is increasingly recognized, and their interaction with common variants is an important area of research. Linkage studies have identified several risk loci, including 17q11–17q21 and 7q, but genome-wide significant results are rare. Association studies have also identified common variants, such as those in CNTNAP2, associated with ASD risk. However, the contribution of common variants remains limited, and rare mutations are more likely to be involved in ASD pathogenesis. Overall, the genetic basis of ASDs is complex, involving both rare and common variants. Understanding the interaction between these variants and environmental factors is crucial for developing effective interventions. Future research will focus on identifying the specific molecular mechanisms underlying ASDs and improving the accuracy of genetic risk assessments.