Causes of Keshan-Beck disease (KBD) are still being probed and monitored in China. Relationships between trace elements from eco-environmental systems and KBD are poorly understood although relationships between environmental Se and human health have received extensive attention. In order to investigate relationships between eco-environmental geochemistry and KBD, we selected the Chousang KBD area in Yao County, Shaanxi Province, China, as an example of a prevailing KBD area applying I-Se-rich salts instead of utilizing Se-rich fertilisers on food crops to prevent local residents from developing KBD before 1995. Environmentally geochemical samples (rocks, soils, plants and children's hair) were collected from the Chousang KBD area. Soils in the study area contain 0.11 +/- 0.02 microgram Se g-1, 0.75 +/- 0.11 microgram Mo g-1, and 34.5 +/- 1.5 micrograms B g-1 on average, indicating that the study area is a deficient-Se-Mo-B area. Se (0.07 +/- 0.007 microgram g-1), Mo (0.35 +/- 0.09 microgram g-1) and B (3 +/- 0 micrograms g-1) contents are low in wheat and corn used as a daily main food staple of local inhabitants. It is indicated that the study area is deficient in environmental Se-Mo-B for the local residents. Se contents of children's hair from the Yangyuan Elementary School in the study area range from 0.09 to 0.26 microgram Se g-1 with an average of 0.165 +/- 0.05 microgram Se g-1 (n = 10) in this KBD endemic area. Due to the low levels of Se, Mo and B available in soils and rocks, crops including wheat and corn are deficient in these elements, accordingly, the deficiency of Se, Mo and B in this area may be linked to the daily consumption of wheat and corn deficient in Se, Mo and B. Therefore, local inhabitants should be encouraged to fertilise mixtures of Se, Mo and B on crop plants in order to avoid development of KBD and guarantee a good harvest of crops.