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The origin of Echinocereus x lloydii BRITT. & ROSE, pro sp. (Lloyd’s Hedgehog Cactus) was investigated using comparative morphology, cytology, biochemistry, and particularly, artificial hybridization. Numerous artificial crosses between the putative parents E. coccineus ENGELM. (a species of claret-up cactus) and E. dasyacanthus ENGELM. (Texas Rainbow Cactus) were successful, resulting in the production of hundreds of seeds with hybrid embryos. The F1 hybrid progeny (i.e., synthetic E. x lloydii) grew to sexual maturity in about four and one-half years, whereupon successful backcrosses and F2 generation hybrids were also obtained. The known F1 hybrids closely approximated natural E. x lloydii. The fertility of these synthetic E. x lloydii was high, like their natural counterparts. The populations of E. x lloydii in Pecos County, Texas are inferred to have originated as the result of natural interspecific hybridization. It is assumed that E. x lloydii or similar plants may arise wherever the parental taxa grow sympatrically.