Abstract: A ballpoint pen with cap has an overall length which is substantially equal to a conventional credit card enabling the pen to fit snugly in a credit card receiving pocket of a pocket book. The pen has a thin, flat body containing a writing cartridge and having opposite side edges diverging rearward in plan from a front writing end to provide a broad, flat, blade-like, hand engaging rear portion. The body also tapers in thickness as it extends outward to opposite side and rear edges forming a narrow, peripheral insertion edge. The rear end is straight and the cap is rectangular so that, when assembled, opposite ends of the pen have straight edges extending substantially perpendicularly to a longitudinal axis of the body. The body has a lateral supporting and guiding lobe for engagement with a writer's hand in different positions to facilitate a fluid writing action with different pen grips.