Technical Abstract: Melon (Cucumis melo L.) is a fresh vegetable and dessert fruit that may also be cooked or dried, processed for juice and flavoring, and the seeds of which are a source of high quality cooking oil and high protein seed meal. Melon production throughout many parts of the world is now threatened by Cucurbit yellow stunting disorder crinivirus (CYSDV) that may occur in tropical and sub-tropical areas favorable to its whitefly vector. CYSDV is transmitted by sweet potato whitefly, Bemisia tabaci Gennadius, biotypes A, B and Q. CYSDV first appeared in the 1980s in the United Arab Emirates, and emerged on melon in the Yuma, Ariz. and Imperial Valley, Calif. region, as well as western Mexico during the Fall season of 2006. Inheritance of resistance to CYSDV in PI 313970, C. melo var. acidulus, a salad type melon from India, was studied in three, naturally infected, replicated field tests in Imperial Valley during the Fall seasons of 2007 and 2008, and the Spring season of 2009. Resistance in PI 313970 was recessive: all F1 PI 313970 (PI) x susceptible ‘Top Mark’ (TM) and BCTM individuals were susceptible, and the F2 and BCPI segregated accordingly. Frequency distributions of CYSDV symptom severity ratings suggested one or two major recessive genes and, perhaps, additional modifying genes in PI 313970 for resistance to CYSDV. PI 313970 was, however, observed to be variable for resistance; a few plants in each test expressed distinct symptoms of CYSDV infection and its frequency distributions overlapped those of ‘Top Mark’. This variation may be random or represent genetic variation selectable for uniform reaction to infection by CYSDV. The resistance expressed by PI 313970 does not confer immunity to infection; CYSDV was detected in asymptomatic plants of PI 313970.