Charity organizations often use mailed requests to solicit donations from the public. This is not an efficient way to raise large amounts of money. The challenge addressed in this study was to use social psychology's knowledge of helping processes to make mailed requests more effective. Two constructs were identified as possibly useful: empathy and perceived effectiveness of helping. These were manipulated in a field experiment in a 2 x 2 x 2 factorial design (two levels of empathy, two of need extent, and two of need persistence--the last two factors operationalized perceived effectiveness). Letter soliciting donations to a well-known charity were mailed to a random sample of 2648 people in Perth, Western Australia. Manipulations of the three variables were embedded in the letters. The two effectiveness manipulations produced significant main effects, whereas the empathy manipulation was ineffective. We argue that social psychology's knowledge of helping processes is too confined to narrow, theoretical, laboratory-based phenomena to be directly and immediately applicable to the practices of charities.