Importing LARGE quantities of data.
If you have trouble importing large data files, try the following.
The appendix below indicates the php.ini settings and where/how they can be overridden. Some can be overridden in the .htaccess file or some settings can be set in other ways (php.ini, httpd.conf or .htaccess, etc.). Most shared hosts do not allow individuals to make changes to php.ini or httpd.conf files.
That being said however, the php execution limit can be overridden in the .htaccess file which is located at the root of your CiviCRM site. I modified mine to the following and it worked and thus, my large imports worked. I hope this is useful.
Add the max_execution_time setting to the .htaccess file at the site root — a complete example is below. 360 is in seconds so, in this case, PHP would wait for 6 minutes before timing out. Up it as you feel it's needed for your case.
Also see http://drupal.org/node/29268 .