One and a half years after the devastating earthquake in Armenia in 1988, 231 children from three cities at increasing distances from the epicentre were randomly screened in their schools to determine the frequency and severity of post-traumatic stress reactions, using the Children's Post-traumatic Stress Disorder Reaction Index (CPTSD-RI). A systematic clinical assessment of PTSD based on DSM-III-R criteria was also conducted on approximately half of this sample. A high CPTSD-RI score was strongly correlated with a clinical diagnosis of PTSD. A strong positive correlation was found between proximity to the epicentre and overall severity of post-traumatic stress reaction, as well as severity of core component symptoms of PTSD. High rates of chronic, severe post-traumatic stress reactions were found among children in the two most damaged cities, Spitak and Gumri. Analyses controlling for exposure revealed that girls reported more persistent fears than boys. These findings indicate that after catastrophic natural disaster, post-traumatic reactions in children may reach epidemic proportions, remain high for a prolonged period, and jeopardise the well-being of the child population of a large region. Systematic screening of children for PTSD can provide critical information for a rational public mental health programme after such a disaster.