After graduating from medical school, Hammer extended earlier entrepreneurial ventures with a successful business importing many goods from and exporting pharmaceuticals to the newly formed Soviet Union, together with his younger brother Victor. According to Hammer, on his initial trip, he took $60,000 in medical supplies to aid in a typhus epidemic and made a deal with Lenin for furs and caviar in exchange for a shipment of surplus American wheat. He moved to the USSR in the 1920s to oversee these operations, especially his large business manufacturing and exporting pens and pencils.