Taiwan-Brunei-China-Malaysia-Philippines-Vietnam: involved in complex dispute over the Spratly Islands in the South China Sea that are thought to have large oil and natural gas reserves, as well as being located amidst prime fishing grounds and busy commercial shipping traffic; the Spratly Islands also are in a strategic position for establishing a military presence to monitor activity in the South China Sea; the 2002 "Declaration on the Conduct of Parties in the South China Sea" has eased tensions but falls short of a legally binding "code of conduct" desired by several of the disputants

Taiwan-China-Philippines: border dispute over the Scarborough Reef in the South China Sea; Scarborough Reef, like the Spratly Islands, is strategically located and is surrounded by abundant fishing grounds; it may also be ripe for oil and natural gas exploration

Taiwan-China-Vietnam: the Paracel Islands are occupied by China but claimed by Taiwan and Vietnam

Taiwan-Japan-China: in 2003, China and Taiwan became more vocal in rejecting both Japan's claims to the uninhabited islands of the Senkaku-shoto (Diaoyu Tai) and Japan's unilaterally declared exclusive economic zone in the East China Sea where all parties engage in hydrocarbon prospecting; Senkaku-shoto is situated near key shipping lanes, rich fishing grounds, and possibly significant oil and natural gas reserves

Brazil-Bolivia: the Roboré Accord of March 29, 1958 placed the long-disputed Isla Suárez/Ilha de Guajará-Mirim, a fluvial island on the Río Mamoré, between the two towns of Guajará-Mirim (Brazil) and Guayaramerin (Bolivia), under Bolivian administration but did not resolve the sovereignty dispute

Brazil-Colombia: contraband smuggling (narcotics and arms), illegal migration, trafficking in animals, plants, lumber, illegal exploitation of mineral resources, and incursions by Colombian insurgent/narco-terrorists groups in the area remain problematic issues

Brazil-Uruguay: the uncontested boundary dispute between Brazil and Uruguay over Arroyo de la Invernada triangle and sovereignty over Isla Brasilera leaves the tripoint with Argentina in question; smuggling of firearms and narcotics continues to be an issue along the Uruguay-Brazil border

Brazil-Venezuela: Colombian-organized illegal narcotics and paramilitary activities penetrate Brazil's border region with Venezuela

Cameroon-Central African Republic: Cameroon has deployed military troops to the border to counter intrusions from armed militias and bandits
 
Cameroon-Nigeria: Nigeria recognized Cameroon's sovereignty over the Bakassi Peninsula in 2006 and in completed the transfer of administration in 2013, although there are occasional, mostly local disputes in the area; the the majority of the land boundary was demarcated by 2019 with UN assistance, although there are few disagreements on the precise location of the boundary; the porous border is susceptible to crossings by the Boko Haram and Islamic State of Iraq and ash-Sham - West Africa terrorist groups, both of which operate in Northern Nigeria