Summary: The impact of using different lossless compression algorithms when compressing biometric iris sample data from several public iris databases is investigated. In particular, the application of dedicated lossless image codecs (lossless JPEG, JPEG-LS, PNG, and GIF), lossless variants of lossy codecs (JPEG2000, JPEG XR, and SPIHT), and a few general purpose file compression schemes is compared. We specifically focus on polar iris images (as a result after iris detection, iris extraction, and mapping to polar coordinates). The results are discussed in the light of the recent ISO/IEC FDIS 19794-6 standard and IREX recommendations.