A program in which the need for a visa is waived for entry to the USA if the traveller meets a number of conditions. This program does not apply to travellers resident in countries adjascent to the US, who do not need a visa.

Conditions

The traveller must:

  1. be a citizen of one of the following countries:
    The Netherlands, Andorra, Argentina, Austria, Australia, Belgium, Brunei, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, Liechtenstein, Luxembourg, Monaco, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Sweden, Switzerland, the United Kingdom or Uruguay. (Citizens of all other countries must have a visa to enter the United States at any time);
  2. have an current passport valid for six months beyond the end of the visit;
  3. be making the visit for the purpose of a holiday, business trip or transit;
  4. be staying for no more than 90 days;
  5. if entering by air or sea, must have a return or onward ticket and where the onward ticket destination is Mexico, Canada, Bermuda, or the Caribbean the traveller must be a resident of the final destination. People entering the US overland from Canada or Mexico require no onward ticket, but they must be able to show proof at the border that they can afford to pay for the visit;
  6. have never stayed longer than 90 days in the United States after entering without a visa;
  7. have no criminal convictions;
  8. have no previous immigration violations;
  9. not be suffering from any contagious diseases of public health significance.
  10. if entering by air or sea, arrive on a carrier which signed an agreement guaranteeing to transport them out of the U.S. if they are found to be inadmissible or deportable;
  11. waive their right to review or appeal an immigration officer's decision about their admissibility, unless making an application for asylum;
  12. waive their right to challenge deportation, unless making an application for asylum.

Travellers entering initially under the program are allowed to make side trips to Mexico, Canada, Bermuda, or the Caribbean and re-enter the U.S. by any means of transport, as long as the total stay in the region does not exceed 90 days.

sources:
http://foreignborn.com/visas_imm/other_visas/11pilot_program.htm
http://www.usemb.nl/cnvviwap.htm