The Rapid DNA Lib Prep kit provides a streamlined and efficient method to construct DNA library for next generation sequencing (NGS) with Illumina ^(R) platforms. The entire protocol can be completed in 2 hours. Starting from fragmented input-DNA (1 – 1000 ng), the kit contains all the enzymes and buffers for end-preparation, adapter ligation and library amplification. To simplify the workflow, the fragmented DNA is end-repaired and adenylated during the initial step. The kit can be conveniently used for construction of PCR-free libraries from 100 ng of high-quality fragmented genomic DNA, or 10 ng of circulating cell-free DNA (cfDNA). PCR primers provided in the kit are optional for users who prefer self-selected high-fidelity DNA polymerases in the library amplification.