The paper introduces the oligo package, a flexible and comprehensive tool for preprocessing oligonucleotide microarray data. The package is designed to address the limitations of existing tools by providing a unified framework that supports a wide range of applications and manufacturers. Based on the BioConductor principles of transparency, reproducibility, and efficiency, oligo extends existing tools and leverages existing code for visualization, data access, and preprocessing routines. It supports feature-level data for different applications and manufacturers, such as Affymetrix and NimbleGen arrays. The package includes structures to simplify usage and interaction with other packages, and it interfaces with other BioConductor tools for downstream analysis. The paper demonstrates the package's capabilities through various applications, including gene expression data preprocessing, genotype calls from SNP arrays, exon data preprocessing, and interfacing with other BioConductor packages for tiling array analysis. The oligo package is freely available through BioConductor and can be used to improve the efficiency and consistency of microarray data processing.The paper introduces the oligo package, a flexible and comprehensive tool for preprocessing oligonucleotide microarray data. The package is designed to address the limitations of existing tools by providing a unified framework that supports a wide range of applications and manufacturers. Based on the BioConductor principles of transparency, reproducibility, and efficiency, oligo extends existing tools and leverages existing code for visualization, data access, and preprocessing routines. It supports feature-level data for different applications and manufacturers, such as Affymetrix and NimbleGen arrays. The package includes structures to simplify usage and interaction with other packages, and it interfaces with other BioConductor tools for downstream analysis. The paper demonstrates the package's capabilities through various applications, including gene expression data preprocessing, genotype calls from SNP arrays, exon data preprocessing, and interfacing with other BioConductor packages for tiling array analysis. The oligo package is freely available through BioConductor and can be used to improve the efficiency and consistency of microarray data processing.