Microarrays-high-throughput platforms for analyzing the gene expression and features of total genomic DNA, among other applications-are gaining in popularity as researchers discover ever more uses for their unbiased and broad feature sets. At present, microarray analyses are limited by the number of individual features that can be placed on each array. Here we describe a double-tiling method that significantly increases the number of sequences present on an array, and we show that successful transcriptional profiling is possible and straightforward with such arrays. With this method, we and others can save money and precious samples by using fewer arrays to cover a region, or can carry out investigations at significantly higher resolution without incurring prohibitive costs or increasing the amount of sample required for the experiment.