[Cameron]

Thanks for the fast reply

my advanced_search.tpl file now contains

<select name="in_category">
<option value="">All</option>
{section name=cat_num loop=$categories_level_1}
<option value="{ $categories_level_1[cat_num].categoryid}" {if $smarty.get.in_category eq $categories_level_1[cat_num].categoryid or $cat eq $categories_level_1[cat_num].categoryid}selected{/if}>
{$categories_level_1[cat_num].category|escape}
</option>

{section name=cat_num1 loop=$categories_level_2}
{if $categories_level_2[cat_num][0][cat_num1].categoryid ne ""}<option value="{ $categories_level_2[cat_num][0][cat_num1].categoryid}" {if $smarty.get.in_category eq $categories_level_2[cat_num][0][cat_num1].categoryid or $cat eq $categories_level_2[cat_num][0][cat_num1].categoryid}selected{/if}>
{$categories_level_2[cat_num][0][cat_num1].category_name|escape}
</option>{/if}
{/section}

{/section}
</select>

...but, the categories still don't show. I also tried changing
{$categories_level_1[cat_num].category|escape}
to
{$categories_level_1[cat_num].category_name|escape}
but that didn't help either.

I'm stumped. Could I have gone wrong with putting together the code for categories.php?