A device for automatic injection of a product into an injection site, the product being carried by a container having an open proximal end and a substantially closed distal end and having a reservoir defined therebetween, and a needle provided at the distal end and in fluid communication with the reservoir to provide an outlet port for the product from the container, and a piston provided in the container and movable with respect with the container, the movement of the piston causing the product to be expelled from the container through the needle, said device comprising: - a housing having a general cylindrical shape for the container, the container being movable relative to said housing between an initial position, in which a tip of the needle does not extend beyond a distal end of said housing and in which the container is in one of a passive state and an active state, to an insertion position, distally spaced relative to said initial position and in which the tip of the needle extends beyond said distal end of said housing, movement of the container out of its initial position being prevented when the container is in its passive state, and being permitted when the container is in its active state, and - a safety shield coupled to said housing for movement between a first position and a second position in which the tip of the needle does not extend beyond a distal end of said safety shield, movement of said safety shield out of its first position placing the container in its active state, said safety shield being movable to its second position when the container is in said insertion position, said safety shield being secured against proximal movement when in said second position, - a needle shield being coupled to a deshielder which is coupled with said housing and covering the needle prior to use of said device, removal of said needle shield from the device being with no rotation of said needle shield, characterized in that said deshielder and said housing are provided with guiding means (40, 41) designed to allow the longitudinal translation of the needle shield with respect to said housing while preventing its rotation, when said needle shield is removed from the device. - a housing having a general cylindrical shape for the container, the container being movable relative to said housing between an initial position, in which a tip of the needle does not extend beyond a distal end of said housing and in which the container is in one of a passive state and an active state, to an insertion position, distally spaced relative to said initial position and in which the tip of the needle extends beyond said distal end of said housing, movement of the container out of its initial position being prevented when the container is in its passive state, and being permitted when the container is in its active state, and - a safety shield coupled to said housing for movement between a first position and a second position in which the tip of the needle does not extend beyond a distal end of said safety shield, movement of said safety shield out of its first position placing the container in its active state, said safety shield being movable to its second position when the container is in said insertion position, said safety shield being secured against proximal movement when in said second position, - a needle shield being coupled to a deshielder which is coupled with said housing and covering the needle prior to use of said device, removal of said needle shield from the device being with no rotation of said needle shield,