Look for business travel costs to increase this year, industry watchers say. Among the causes: Higher gas prices, higher taxes and increased demand.

Domestically, airline tickets are expected to go up 6%, hotel rates 9% and rental car fees 5%, according to the National Business Travel Association's annual forecast. The report, Business Travel Overview and Cost Forecast 2006, is available for purchase at nbta.org.

A survey by American Express also predicts increases worldwide. Economy fares for short-haul flights will increase 3% to 6%, while international and longer trips will go up 3% to 5%, the company's travel management unit predicts. Hotel rates will increase worldwide 3% to 5% at higher-priced properties and 1% to 3% at those in the midrange category.

Final figures for 2005 aren't available yet, but the Travel Industry Association of America estimates expenditures for combined business and leisure travel nationwide grew
8% last year, topping $645 billion. TIAA predicts business travel spending this year will rise 1.6% domestically, compared with 1% for 2005.