Nowadays the term "OL (office lady)" is seen as semiderogatory (about time, too), and some companies have trashed it completely and started using simply jyosei shain (women employees). This is to differentiate them from sogoshoku (general worker), which is not gender-specific but is used to describe women who take on the same responsibilities as their male colleagues.
What a heap of distinctions for working women, compared to men who can just say, "Oh, I'm a salaryman," and be done with it. It seems as though the Japanese corporate world is still uncertain about how to treat the women in its midst. Some of the older generation of bucho (section managers) say that OLs are just koshikake (seat-warmers), meaning they're occupying a seat in the company until it's time to quit and get married, so why treat them seriously at all?
The roots of discrimination date back to immediately after World War II when female office workers were called "BG" (business girl). Apparently, the term went out of style in the '60s after someone pointed out that it implied prostitution. But whether they were called BGs or OLs, their work remains the same. Besides taking on the bulk of secretarial duties, the twin pillars of their job description are ochakumi (making and serving tea) and kopii-tori (making copies). In recent years, deita nyuryoku (data input) has been added, spawning the No. 1 OL shokugyobyo (occupational hazard) of katakori (shoulder cramps).