Lao PDR is recognized as one of the centers of genetic diversity of traditional rice varieties, with the number of traditional Lao varieties which have been collected and are now being maintained in the International Rice Germplasm Bank, being among the highest any individual country in the world. It is recognized that some characteristics of the traditional varieties have the potential to make a significant contribution to future rice breeding programs. Understanding the nature of the genetic diversity, within and between populations, can help make informed conservation decisions, in situ and ex situ. The objective of this study was to determine genetic diversity, within and between populations, of a collection of a local Lao rice variety called Khao Kai Noi (Small chicken rice). Khao Kai Noi is a tropical japonica, or javanica type. A total of 26 populations of the variety, collected from farmers in the two northeastern provinces of Houahanh and Xieng Khoung in Lao PRD, were the focus of the study. Three groups of Khao Kai Noi have been defined, based on the color of their glumes - Kai Noi Deng (red), Kai Noi Lai (striped) and Kai Noi Leuang (yellow). Plants grown from the seed were evaluated for their morphological (qualitative and quantitative) characters, milling quality, eating quality, aroma, and seed viability. The 26 populations involved in the study were grown in the 2011 wet season at the Rice and Cash Crops Research Center (RCCRC) in Vientiane Municipality.Variation was found within and between population in grain characteristics, such as color of husk and apiculus, from dark red to dark purple and dark brown, spikelet awning and 100-grain weight. There was no variation within and between populations in color of the grain seed coat, indicating that all 3 groups of Khao Kai Noi are entirely glutinous (waxy). There was only small variability in the color of stigma, sterile lemma and spikelet, but no variability in color and shape of ligules, leaf blades, leaf sheaths and auricles. The assessment of eating quality of the three types found that Kai Noi Lai was softer, more aromatic and tastier that the other two types; it also better retained its eating quality on cooling. All three types lost all aroma after three hours cooking, but retained their softness. From 26 samples, 6 gave relatively high yields (2,800-3,500 kg/ha) when compared with check varieties. The combination of higher altitude and cooler climate where Kao Kai Noi
is grown, probably contributes to their growth and superior quality.