Despite the similarities between the Nordic countries with regard to s
ocial and political structures, major differences in grass roots parti
cipation are found. Participation is highest in Sweden and lowest in F
inland, with Denmark, Norway and Iceland falling in between. There are
also striking differences between the countries regarding the relatio
nships between participation and factors as age, gender, education, so
cial class and party choice. Two theories may help us to understand th
ese differences. The first, mobilization theory, claims that grass roo
t participation is used to mobilize new social groups. This theory is
supported by evidence from Denmark, Norway and Iceland. During the 197
0s and the 1980s all three countries experienced political mobilizatio
n of the well-educated. the new middle class and the women. The second
theory, supplement theory, claims that grass root participation is no
thing but an extension of the conventional modes of participation. Thi
s theory is supported in Sweden. The last section of the paper argues
that differences between countries may be explained by differences in
the strength of traditional political organizations.