The arrival (2005) and rapid establishment in Florida of the most devastating disease known to citriculture, namely Huanglongbing or Citrus Greening Disease, has caused dramatic changes to the long-term citrus rootstock breeding program at the University of Florida’s Citrus Research and Education Center (UF-CREC). Since all commercial scion/rootstock combinations have proven to be susceptible to the disease, there is an urgent need to quickly develop improved rootstocks with good horticultural attributes that can mitigate the disease in trees grafted with commercial scions. This report describes our efforts to achieve this goal. Our approach is to rapidly develop and screen a large population of genetically-diverse hybrid rootstock candidates. Multiple available sources of potential rootstock germplasm are being exploited in our efforts. We have identified several good rootstock candidates that are showing improved HLB tolerance. These are now being propagated either by seed or micropropagation as needed for advanced multi-site trials with multiple scions. This research offers potential for the ultimate solution to HLB, leading to sustainable and profitable citriculture in HLB-endemic areas.