We use the Updated Zwicky Catalog of galaxies ( Falco et al .
1999 ) to generate a catalog of groups , by means of a friend-of-friend algorithm .
The groups identified have 4 or more members and a surrounding density contrast , \delta \rho / \rho = 80 .
They cover the region -4 \arcdeg < \delta < 90 \arcdeg , |b| > 20 \arcdeg spanning over the radial velocity range of 2000 km s ^ { -1 } < cz < 15000 km s ^ { -1 } .
The total sample ( hereafter GUZC ) comprises 517 groups .
The correlation length of the total sample is well fitted with a power law \xi ( r ) = ( r / r _ { 0 } ) ^ { \gamma } with parameters r _ { 0 } = 9.0 \pm 0.4 h ^ { -1 } Mpc and \gamma = -1.67 \pm 0.09 for values of r < 70 h ^ { -1 } Mpc , declining to homogeneity at larger scales .

Three subsamples defined by the range of group virial masses { \cal M } were used to have their clustering properties examined throughout the autocorrelation function .
We find an increase of the amplitude of the correlation function according to the group masses which extends the results of the r _ { 0 } - d _ { c } relation for galaxy systems at small d _ { c } .
We obtain r _ { 0 } = 9.5 \pm 0.5 h ^ { -1 } Mpc ( \gamma = -1.81 \pm 0.12 ) , r _ { 0 } = 10.8 \pm 0.7 h ^ { -1 } Mpc ( \gamma = -1.77 \pm 0.17 ) , and r _ { 0 } = 14.1 \pm 1.2 h ^ { -1 } Mpc ( \gamma = -1.65 \pm 0.22 ) for mass ranges 5 \times 10 ^ { 12 } M _ { \odot } < { \cal M } < 4 \times 10 ^ { 14 } M _ { \odot } , 2 \times 10 ^ { 13 } M _ { \odot } < { \cal M } < 4 \times 10 ^ { 14 } M _ { \odot } and 5 \times 10 ^ { 13 } M _ { \odot } < { \cal M } < 4 \times 10 ^ { 14 } M _ { \odot } respectively .

For completeness we have also analyzed a sample of groups obtained from the Southern Sky Redshift Survey ( da Costa et al.1998 ) in the range of virial masses 5 \times 10 ^ { 12 } M _ { \odot } < { \cal M } < 4 \times 10 ^ { 14 } M _ { \odot } to compare the results with those obtained from GUZC .
The correlation function of this sample can be fitted with a power law with parameters r _ { 0 } = 8.4 \pm 1.8 h ^ { -1 } Mpc and \gamma = -2.0 \pm 0.7 .