[en] Cell survival measurements as a function of depth have been reported for three pion beams modulated in different ways. Cultured human cells (line T1) suspended in gelatin medium were used in this investigation. A uniform dose distribution in the peak region was found to produce more cell killing at the distal side of the peak compared to the proximal side. A uniform π^- stopping distribution in the peak region produced more cell killing at the proximal side of the peak compared to the distal side. These two distributions represent the extremes. The optimum dose distribution to obtain uniform biological effect in a broad pion peak region can be acquired by making the dose distribution nearly uniform from the proximal side of the peak to the peak center and then reducing the dose gradually from the peak center to the distal end of the peak. Cell killing in the peak region was more uniform for all three dose distributions when two opposing and overlapping fields were used. Dose distributions to produce uniform cell killing should be checked at higher doses because of the small rate of survival change in the shoulder region compared to the exponential region