He was moved to the intensive care unit of a London hospital Nov. 20 after his condition took a turn for the worse. The investigation into the poisoning follows the Nov. 14 arrest in Canada of an alleged Russian spy.

Although such incidents often are described as "reminiscent of the Soviet era," espionage between Russia and the West never subsided after the Cold War. In fact, spying could be even more common now than before.

Litvinenko, a former officer in the Soviet KGB and its successor, Russian Security Services (FSB), claimed in his 2002 book that the 1999 bombings of apartment blocks in Russia, which led to the second Chechen war, were actually the work of FSB operatives. He became ill after meeting a contact at a London sushi bar to discuss the slaying of Russian investigative journalist Anna Politkovskaya, another well-known critic of President Vladimir Putin's government. Politkovskaya was gunned down by unknown assailants in Moscow on Oct. 7 in an act that human rights organizations have said underscores the risks faced by Russians who question or criticize their government. Friends of Litvinenko's, including former oligarch and Russian dissident Boris Berezovsky, have claimed that Moscow was behind the poisoning, a charge that the Kremlin rejects as "sheer nonsense."

If Litvinenko's poisoning was in fact an assassination attempt by the FSB or one of its surrogates, it shows not only that the spy game between Moscow and the West is alive and well, but that it still can be lethal. The contact Litvinenko was meeting at the sushi bar -- Mario Scaramella, an Italian academic who helped investigate KGB activity in Italy during the Cold War -- reportedly has gone into hiding since the poisoning, suggesting he is afraid for his life as well.

The KGB, the FSB's direct predecessor, used poison to silence dissidents, including in London. In 1978, Georgi Markov, a Bulgarian dissident living in London, died after being injected with a tiny drop of the poison ricin while at a bus stop on his way home. The ricin, administered via the tip of an umbrella, was contained in a tiny metal pellet that experts said could not have been machined in Bulgaria, but could have been made in the Soviet Union. Politkovskaya also was the alleged victim of a poisoning at one time. After she fell seriously ill in 2004 while on her way to cover the school hostage crisis in Beslan, colleagues claimed her illness was an attempted poisoning by Moscow. Perhaps the most blatant example of the poisoning tactic is the case of Ukrainian presidential candidate Viktor Yushchenko, who fell ill from the poison dioxin during his 2004 campaign.

With so much attention focused on the global war on terrorism, it is easy to forget that the FSB and its surrogates continue to collect intelligence in the West on both governmental and nongovernmental Western targets. In fact, with the Cold War military threat greatly diminished, it is possible that espionage has increased. With Moscow and the West less able to gauge each other's intentions by observing troop movements and military procurement, spying is left as a way to keep tabs on the other's activities.

Since Putin -- the former head of the FSB and a career KGB officer before that -- became president of Russia, actions against critics of the regime have increased. This action has been overt, such as shutting down opposition media outlets, as well as covert, such as eliminating journalists and dissidents. In recent years, especially since the Yushchenko poisoning, operatives have been acting with increasing brazenness and with seemingly little fear of the consequences if their cover is blown and the operation exposed.

This climate also presents risks to private organizations such as multinational corporations and nongovernmental organizations that operate in Russia. Unlike government agencies and embassies, these actors have much less diplomatic and legal protection from the efforts of the Russian security services.