Single-molecule FISH (smFISH) has been the gold standard for quantifying individual transcript abundances. Here, we scale up multiplexed smFISH to the transcriptome level and profile 10,212 different mRNAs from mouse fibroblast and embryonic stem cells. This method, called RNA sequential probing of targets (SPOTs), provides an accurate, flexible, and low-cost alternative to sequencing for profiling transcriptomes.