A list box is scrollable if you specify the rows property or the height property, and there is no enough to show all list items.
<listbox width="250px" rows="4">
<listhead>
<listheader label="Name" sort="auto"/>
<listheader label="Gender" sort="auto"/>
</listhead>
<listitem>
<listcell label="Mary"/>
<listcell label="FEMALE"/>
</listitem>
<listitem>
<listcell label="John"/>
<listcell label="MALE"/>
</listitem>
<listitem>
<listcell label="Jane"/>
<listcell label="FEMALE"/>
</listitem>
<listitem>
<listcell label="Henry"/>
<listcell label="MALE"/>
</listitem>
<listitem>
<listcell label="Michelle"/>
<listcell label="FEMALE"/>
</listitem>
</listbox>
The rows property is used to control how many rows are visible. By setting it to zero, the list box will resize itself to hold as many as items if possible.