This research studied the effects of various types of writing instruments on handwriting performance from the man-machine systems viewpoint. Different types of writing instruments represent differential levels of point reliability which affects the feedback stability needed for efficient performance. Four typesof writing instruments were selected: ballpens, pencils, feltpens, and fountainpens. The writing time and writing pressure were the dependent variables, measured by a PDP-8 computer for a total of 48 subjects writing a series of lower-case "a's." Results showed the ball pens to generate the least and fountainpens the most writing time, and the feltpens to result in the least and the ballpens the most writing pressure. A ranking of writing time for the four instruments experimentally confirmed a previous preferential ranking of the same writing instruments. Significant differences were found among the instruments with respect to both time and pressure. The writing speed of the males was significantly faster than that of the females, while the writing pressure showed no difference by sex.