AbstractHavana syndrome is a cluster of distressing symptoms (including hearing problems, dizziness, nausea, and headaches) first reported in 2016 among employees of the US and Canadian embassies in Havana, Cuba, and subsequently observed in individuals in other countries. The most frequently cited potential causes of the syndrome have been exposure to microwave radiation, insecticides, and psychogenic factors.The analysis presented in this paper demonstrates that, in addition to the possible scenario of organophosphate insecticide poisoning (section 3.2) and a resulting psychogenic response (section 3.3), a microwave mechanism for Havana syndrome incidents (the Frey effect) is highly improbable (sections 5–7), a conclusion supported by previous research.The most likely physical cause of these incidents is the laser-induced optoacoustic effect (sections 6–7). Laser-directed energy technologies are considerably more compact, user-friendly, effective, and covert than alternative mechanisms, even when deployed against individuals in confined spaces (section 6.2).The accessibility of laser technologies means they could be employed by a range of state and non-state actors, not solely by Russian intelligence services, which have been most frequently implicated in investigations (section 6).It is recommended that collective and individual diagnostic methods for potential exposures to at-risk personnel be enhanced by utilizing sensors operating in the infrared, ultraviolet, and visible light spectrums, in addition to the microwave range (sections 6.3.2, 7).