NGC 2355 is an old open cluster in the outer part of the galactic disk ( l = 203 \aas@@fstack { \circ } 4 , b = +11 \aas@@fstack { \circ } 8 ) which has been little studied until now .
This paper presents the first astrometric and spectroscopic investigation of this cluster .
We have measured precise absolute proper motions from old Carte du Ciel plates , POSS-I plates and recent CCD observations obtained with the Bordeaux meridian circle .
The proper motion data reveal 38 highly probable cluster members down to B _ { \mathrm { lim } } = 15 mag within 7 ^ { \prime } of the cluster center .
We have also obtained ELODIE high resolution spectra for 24 stars .
Seventeen of them are confirmed to be members of the cluster on the basis of radial velocity .
Eight of them are fast rotating turnoff stars for which the projected rotational velocity has been determined .
The spectroscopic observations have also provided estimates of the physical parameters T _ { \mathrm { eff } } , \log g, \mathrm { [ Fe / H ] } ,M _ { \mathrm { V } } of the 24 target stars .
Two stragglers have been identified in the cluster .
Combining our astrometric and spectroscopic results with previous UBV photometry and recent JHK _ { s } photometry from the 2MASS survey we have derived the fundamental properties of the cluster : metallicity , age , distance , size , spatial velocity and orbit .