The cost of coverage varies, with some insurers charging memberships to cover all trips in a year

In screening a potential travel insurer, begin with some fundamental questions: If I have a problem, how do I access help? If an emergency arises, where would I receive care? In the nearest facility? A hospital of my choosing? Would I be transported home? Do you have a network of doctors trained in Western-style medicine who ideally speak English?The good news is that for most major travel insurers today, access to care and response times are points of pride. CSA, for instance, says it provides travelers with a 24-hour emergency toll-free number that is answered within 20 seconds, and local numbers that can be called collect. Global Rescue LLC, a Boston-based travel specialist, says its members who call in are connected immediately with, among others, critical-care paramedics or nurses. The pany says that in many parts of the world, field rescue and evacuation can occur the same day. Medical evacuation is a traveler's largest financial risk, says Dan Skilken, president and chief executive of TripInsurance in Monte Sereno, Calif. As such, be sure your coverage matches your destination. In other words, if you're traveling in Mexico or Central America and if you need to be flown to the U.S. with a doctor on a private jet budget for $50,000 in evacuation expenses, Mr. Skilken says. If you are traveling to Western Europe, then $100,000 to $150,000 will get you home. If you are traveling in Asia, you need at least $200,000, he estimates.Comparing plans and rates online is essential; so-called aggregator sites make the job easier. Both InsureMyTrip , based in Warwick, R.I., and SquareMouth , in St. Petersburg, Fla., allow you to enter details about your travels and pare different policies. The cost of coverage varies, with some insurers charging memberships to cover all trips in a year, while others insure by the trip. An individual seven-day medical membership at Global Rescue is $119, and a 14-day medical membership is $159. If your home is in Massachusetts and you'll be doing a 10-day trip to Mexico in April, and then traveling to Colorado in May for a long weekend of hiking, and planning on fishing in Canada at some point this summer, the short-term memberships quickly cost more than an annual medical membership, which is $329.