The residue-residue contacts in 61 globular protein molecules were studied by using CSU software．The aim is to find the ability of forming the short-range and long-range residue-residue contacts for several residues．It is found that it is easy to form the long-range residue-residue contacts for Leu

Val

Ile

Met

Phe

Tyr

Cys

Trp residues

and it is difficult to form the long-range residue-residue contacts for Glu

Gln

Asp

Asn

Lys

Ser

Arg

Pro residues．The residuce are called residues hydrophobic (H) and hydrophilic (P) residues

respectively

and the other residues is called neutral residue (N)．The average number of long-range contacts per residue is 6.03

4.43 and 3.64 for H

N and P residues respectively．However

the average number of short-range contacts per residue ranges from 2.34 to 2.85

and it is almost no difference among those residues in forming the short-range contacts. Our research may provide some insights into the stability and folding of protein molecules.