Although Honduras lies solidly in the tropics, large sectors of the country will seem anything but tropical to you. Tegucigalpa and the highlands perch at altitudes of 2,000 to 4,000 feet and can feel brisk in the evening. Bring along at least a lightweight jacket and a pair of long trousers to supplement your tropical cabana wear if you plan to travel anywhere outside the Bay Islands, San Pedro Sula, and the Caribbean or Pacific coasts.
For sightseeing, casual clothing and good walking shoes are desirable and appropriate. Honduras has several colonial communities—Copán Ruinas, Santa Rosa de Copán, Gracias, and Comayagua—with cobblestone streets. They're charming, to be sure, but if you wear a flimsy pair of shoes, you'll feel every stone in the soles of your feet. Most cities don't require formal clothes, even for evenings. If you're doing business in Honduras, you'll need the same attire you would wear in U.S. and European cities: for men, suits and ties; for women, suits for day wear, and for evening, depending on the occasion—ask your host or hostess—a cocktail dress or just a nice suit with a dressy blouse.
Travel in rain-forest areas—the Caribbean coast or the Mosquitía—will require long-sleeve shirts, long pants, socks, sneakers, a hat, a light waterproof jacket, a bathing suit (if you want to swim), sunscreen, and insect repellent. You can never have too many large resealable plastic bags (bring a whole box), which are ideal for storing film, protecting official documents from rain and damp, and quarantining stinky socks.
Other useful items include a travel flashlight and extra batteries, a pocketknife with a bottle opener (put it in your checked luggage), a medical kit, binoculars, and a calculator to help with currency conversions. A sarong or light cotton blanket can have many uses: beach towel, picnic blanket, and cushion for hard seats. Most important, always travel with tissues or a roll of toilet paper as sometimes it's difficult to find in local restrooms.