The medial prefrontal cortex (mPFC) participates in the top-down control to subcortical limbic circuits and is suggested to be responsible for decision-making. The elevated plus-maze test is a widely used test for measuring anxiety-related behavior of rodents. In this test, animals often dip their heads and shoulders over the open arms from the center area of the maze, when they make decision to enter the open arm or avoid. We examined multi-unit activity in the mPFC during head-dipping behavior in the elevated plus-maze. The subjects were male SD rats. Stainless steel wires (two wires of 50 μm in diameter) were implanted in the mPFC of rats. Rats were allowed to recover for one week before recoding. The experiments were performed in a dark room illuminated by red lighting. A video camera was fixed above the elevated plus-maze. The maze was made of two open arms (50Χ10 cm) and two closed arms (50Χ10Χ30 cm) extending from a central platform (10Χ10 cm), and was elevated 50 cm above the floor. Rats were placed in the maze for 10 min. Multi-unit activity was recorded using a wireless multi-unit recording system. The activity was amplified, filtered and continuously sampled. Neuronal and behavioral data were continuously acquired over the experimental periods and stored for further analyses. Head-dipping behavior was classified into two types according to subsequent behavior to enter the open arm and avoid. The number of firing in mPFC neurons showed increase in firing before entering the open arms. Thus, the neuronal activity in the mPFC may be related to positive decision-making such as open arm entries.