The civil war in Chad has become one of the most protracted conflicts on the African continent. Its gradual internationalization led to the participation of three foreign military contingents in an internal armed confrontation Libya has taken an active military part in the civil war in Chad since 1972. There were several indications in certain studies about the use of chemical weapons by the Libyan troops. In the realities of the 1980s, these allegations could be true, or they could be an element of some information campaign against Libya. The purpose of this article is to verify the reports of the use of chemical weapons in Chad. Sources, methods. The sources for the study were the UN documents, declassified CIA materials and media reports. Cross-analysis of the documents, as well as the historical reconstruction of background events were carried out. Discussion of the results and conclusions. The analysis of the sources showed that, to date, no material evidence of the use of chemical weapons by Libyan troops in Chad has been found. There were no testimonies of direct witnesses and victims. No investigations have been carried out. Two sources of dissemination of information about the use of chemical weapons in northern Chad have been identified. The first one is the representatives of one of the participants in the civil war, Hissene Habré, who held the post of president in N'Djamena and fought against the Libyan troops. Representatives of H. Habré made such statements in December 1986. They cannot be considered reliable. In this way, one of the parties to the civil war wanted to show that Chad was the victim of the aggression with the use of weapons prohibited by the Geneva Protocol of 1925. However, it was established that in 1986 Libya did not possess chemical weapons. The second source is the CIA reports retransmitted to the public space in September 1987 about the alleged deliveries of chemical weapons to Libya from Iran. The reliability of these reports is doubtful. The «Iranian trace» has also not been proven. In 1987, during the Iran-Iraq war (1980-1988), chemical weapons were used against Iran, but the military-chemical potential of Iran itself has not been established. However, such an accusation organically fit into the policy of containment of «rogue states» pursued by the administration of US President Ronald Reagan. In this article, cross-analysis methods have been tested. They have shown their effectiveness in retrospective investigations.