Although remaining with one company for 20 years is less common in today's workforce, it should not necessarily be considered an obstacle when seeking a new position. Focus on the positive characteristics, such as loyalty, competency and job satisfaction. Most prospective employers value these qualities. Highlighting the changes you experienced over 20 years demonstrates that you have not stagnated during this time and draws attention to the positive aspects of long-term dedication to the company.
Changes to the Company
Your company has probably gone through many changes since you first started working there. If the company has grown substantially, think of the contributions you made that helped the expansion and include these in your resume. For example, if you were responsible for recruiting new clients and your success in this area yielded significant results, describe this in your resume under the heading of "personal accomplishments." Similarly, if new products were introduced or new methods of solicitation were adopted, include the role you played in the implementation process.
Changes in Personnel
New top-level managers usually impose their personal style on the company and influence the way the business is run. It's important to show your adaptability, so include a section that displays your superior interpersonal skills and your ability to work well with a variety of different managers having significantly different approaches. Your relationships with co-workers are equally important, so if you've had the opportunity to work with a wide variety of people it's definitely worth mentioning.
Changes in Technology
Prospective employers might be concerned that you stayed with one company because you feared change or that you're not computer savvy. They need to be shown how you've kept current with all the new technologies introduced in the last 20 years. If you've recently taken courses or workshops, or if you subscribe to professional journals, especially if they are related to computer programs, create a section in the resume describing your updated skills. Your resume should demonstrate your ability to learn new things.
Personal Growth and Development
Most importantly, highlight any changes in job title or responsibilities that you've had over the years. Remaining at one company for 20 years won't be regarded with suspicion if you've received regular promotions and worked your way up the corporate ladder. If your job title did not change over the years, but your job responsibilities increased, arrange your resume to highlight the additional responsibilities you assumed over the years. For example, if you successfully trained or mentored new staff, you show leadership skills which belong on your resume.