A cap for a writing instrument is provided with a suffocation preventive construction. Thus, if a curious child or the like should accidentally swallow the cap and the cap lodges in the child's throat or bronchus, a sufficient flow of air is provided to avoid suffocation. Particularly, a cap for a writing implement of a double-tube construction is provided with an air communicating portion positioned in an inner peripheral surface of an outer tube having open front and rear portions. An inner tube having a closed end is held coaxially within the outer tube, and a predetermined clearance is provided to enable communication between the air communicating portion, defined by space between the outer tube and the inner tube, and a front-end opening of the outer tube. The predetermined clearance is provided between an inclined lower end of a tapered portion provided in a front-end opening of the inner tube and the inner peripheral surface of the outer tube, whereby the permeability of the cap is not impaired by ink adhered to the tapered portion during the process of mounting of the cap to the axial tube of the writing implement.

A removable cap for receiving a writing implement includes a hollow tubular member with a closing wall at one end and an opening at the other end. The closing wall possesses three radial rib members and a central interior land portion which define three arcuately shaped apertures which are configured to allow air to communicate with the interior of the cap to dry residual ink on the writing point of the implement.