Abstract: A party balloon (10) includes an expansible membrane with an inlet port (15) to allow entry of gas upon inflation and an illumination device having a light emitting diode (LED) (50) powered by at least one battery (54) and mounted inside the balloon (10). The illumination device (50) has a projection (58) that is attached to the expansible membrane, inside the balloon, by a clip or O-ring (59), fitted onto the projection (58) from outside the balloon. A strip of insulating material (53) is initially located between the battery or batteries (54) and the LED (50) and is capable of being withdrawn, prior to or upon inflation of the balloon (10), to light up the illumination device and the balloon.