Constraints/On Delete...

Newbie alert!! :p

I have 2 tables already created

CREATE TABLE "first" (
"name" varchar (100) NOT NULL,
"record_num" SERIAL,
PRIMARY KEY ("record_num"));

CREATE TABLE "second" (
"text" varchar (10) NOT NULL,
"name" int4 REFERENCES "first"("record_num") NOT NULL,
"record_num" SERIAL ,
PRIMARY KEY ("record_num"));

and have records in each. The "name" field in the "second"
table contains data that matches data in the "first". Now,
when I go to delete a row from "first", I'm getting the error:

ERROR: $1 referential integrity violation - key in first still referenced
from second

which I can understand. Now, how can I alter the "first" table
so that when I delete rows from it, the corresponding rows from
the "second" table are deleted as well? I was looking at the
ALTER TABLE syntax but the only thing I saw there was adding a
foreign key. But I already have a foreign key set up by the
REFERENCES in the create definition for the "second" table, yes?
So what do I need to do?

thnx,
Chris