As data accumulate in GenBank, the difficulties of delineating species of Cryptosporidium based on nuclear small subunit ribosomal RNA (ssu rRNA) gene information alone becomes increasingly evident. Here, we summarize currently available evidence suggesting that several ssu rDNA sequences primarily referred to as Cryptosporidium suis (some of them from non-suid hosts) should be considered Cryptosporidium occultus.