Larry Stone and Chester Eskholme founded Professional Ambulance Service in 1969. Both men had strong ties to the Cambridge-Somerville community with Larry bringing medical experience from having served aboard a Naval Hospital ship during Vietnam. Their combined knowledge of the area and the fact that they were two of the only 500 certified Emergency Medical Technicians in Massachusetts created a perfect match for starting an ambulance company. With a single ambulance and an office on the Cambridge-Belmont line, Larry and Chester proudly served all communities that requested their assistance.

Eager to grow, PRO signed an agreement with the City of Cambridge in 1972 to provide back-up ambulance services to the Cambridge Fire Department. With the addition of a second ambulance that year they began to focus their attention on the Boston area. PRO transported patients for Boston City Hospital, multiple nursing facilities, and private residents. The increased call volume necessitated additional ambulances and a second location.

By 1973, Larry and Chester opened another location in the City of Boston. They wanted to serve Boston’s larger facilities, specifically the Children's Hospital. At this time EMS was still in its infancy and few providers were capable of handling specialized transports. The Children’s staff needed to transport critically ill or injured children from outlying facilities back to their hospital for proper care. PRO solved the staff’s dilemma by building a custom ambulance for these transports, thereby securing the Children’s contract.

Throughout the years, PRO recognized steady growth despite increased competition from new providers. PRO's reputation as an EMS leader in the Metro-Boston area was well earned and established by 1979. Even then, Larry and Chester were still regularly working as partners on an ambulance. Tragically, Chester passed away from an aneurysm in 1980 leaving Larry as the sole owner of the business. At this point, Larry brought in his wife Cathy to provide administrative and business support. Eventually, Larry and Cathy would also bring in their three daughters to serve in PRO’s billing department.

In 1986 PRO initiated its Advanced Life Support service. Standing orders, online medical direction, and physician oversight were all handled by a newly formed association of area hospitals, South Middlesex Emergency Medical Services. Physicians from The Cambridge Hospital and Mount Auburn Hospital provided medical control for the paramedics working on the ALS ambulances. By 1988, ALS was available 24 hours a day, 7 days a week.

In 1990 Bill Mergendahl, an EMT and dispatcher at PRO throughout his undergraduate years at Boston University, assumed responsibility for daily operations. Throughout the 1990s business continued with a growing focus placed on City of Cambridge programs for the elderly, youth and under served. During this time, Bill was certified as a paramedic and earned his law degree as he evolved into his current role as CEO with Larry as PRO’s President. Recent years have seen dramatic changes in EMS and at PRO.

After the tragic events of September 11, 2001 a renewed emphasis was placed on emergency preparedness. In response PRO extended its commitment to training and education within the community. In early 2002 PRO began what would become a continuous project to update antiquated systems and equipment taking advantage of state-of-the-art technology whenever possible. These changes enabled PRO to redouble and formalize its efforts in the areas of Continuous Quality Improvement and Staff Development. On May 1st, 2005 the already unique, symbiotic public/private partnership between PRO and the Cambridge Fire Department was greatly enhanced as the Cambridge Fire Department initiated its ALS service.

Today, PRO is still a family owned and operated organization. Several dedicated, long-time employees have helped PRO retain its unique character during a period of ambulance service consolidation. Just as in 1969, the patients and employees are treated as family and the equipment is maintained as if it were their own. More than anyone, Larry knows what it's like to work on an ambulance and understands how important it is to appreciate your job. You'll still find Larry working on an ambulance at a charitable event, a community function, or even a local football game, imparting his values to every newly hired employee.

Today, PRO is still a family owned and operated organization. Several dedicated, long-time employees have helped PRO retain its unique character during a period of ambulance service consolidation. Just as in 1969, the patients and employees are treated as family and the equipment is maintained as if it were their own.