190 countries
196 countries participated in the Copenhagen United Nations Climate Change Conference in 2009.
According to the official COP15 website 193 countries (and numerous NGOs) participated, so the answer to your questions must be Participating FOREIGN countries.
71 countries participated at the 2010 Commonwealth Games.
44 countries participated in the 1924 Summer Olympics. 16 countries participated in the 1924 Winter Olympics.
46 countries participated in the Commonwealth Games in 1990
14 countries participated in the 2011 Cricket World Cup
42 countries participated at the 1970 British and Commonwealth Games.
45 countries participated at the 16th Asian Games in 2010.
There are 208 countries in F.I.f.A.
44 countries participated in the 1924 Summer Olympics. 16 countries participated in the 1924 Winter Olympics.
67 countries first participated in the International Geophysical Year in 1957-1958.
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