More than 100 megalithic jars sites are known from northern Laos each comprising from one to several hundred carved stone jars. While collectively named as ‘the Plain of Jars’, based on the three most accessible and visited sites (Sites 1, 2 and 3), most jar sites are found in mountainous areas in Xieng Khouang province, covering an area of around 7000 km2. In this presentation, we outline the geographical setting in which these sites are located, briefly review previous research, and present the results of research undertaken by the authors in close collaboration with the Department of Heritage, Lao PDR from 2016 to 2020. This research focussed on four megalithic sites, namely, Sites 1, 2, 67 and 52. Site 1 has been excavated on several occasions in the past including two seasons undertaken by our team and comprises 316 jars set around a limestone cave. Site 2 is located some 12 km from Site 1 with jars set atop two knolls. Site 52 was examined as it is geographically distinct from Sites 1 and 2 being located in a mountainous setting. Site 67, which boasts buried stone jars, was excavated in 2020 in a rescue operation. The research at Site 1 revealed evidence of varied mortuary practice around the megaliths, secondary burial of human remains, both in ceramic vessels and bundles of bones as well as primary burial in one instance. While human remains were absent from the other sites excavated, archaeological evidence suggests similar burial practices were followed. The paper will also provide the latest information on the dating of these sites based on radiocarbon results from bone, charcoal and Optically Stimulated Luminescence dating of sediments beneath the megaliths.