The apodyterium was the primary entry in the baths, comprised of a large changing room with cubicles or shelves where citizens could store clothing and other belongings while bathing.

Privately owned slaves, or one hired at the baths, called a capsarius, would look after belongings while citizens enjoyed the pleasures of the baths (apparently thieves found personal affects very tempting). A contemporary Roman schoolbook quotes a wealthy young Roman schoolboy who entered the baths, leaving his slave behind in the apodyterium: "Do not fall asleep, on account of the thieves."

Wealthy free men and women often brought numerous slaves with them as they entered the apodyterium, parading them as displays of social prominence. These slaves would carry various bathing paraphernalia: exercise and bathing garments, sandals, linen towels, and a toilet kit that consisted of anointing oils, perfume, a sponge, and strigils, curved metal instruments used to scrape oil, sweat, and dirt from the body.