array question

Is there any easy way to get this data:

kls_dev=# select * from ary_values;
 agent_name | myval
------------+-------
 a          |     1
 a          |     2
 a          |     3
 b          |     4
 b          |     5
 b          |     6
(6 rows)

to look like this:

kls_dev=# select * from ary_test;
 agent_name |  vals
------------+---------
 a          | {1,2,3}
 b          | {4,5,6}
(2 rows)

In other words, I would like to group by 'agent_name' and then convert
all the 'myvals' associated w/ that agent_name into an array.

I tried a few simple things like this:
kls_dev=# select array_append(myval) from ary_values group by agent_name;

but no luck so far.

Thanks,
Whit