Traditional forensic drug testing labs are familiar with drugs in the form of powders, plants, and pills and have validated procedures in place for testing them. However, bottles and glass with liquid drugs that are colorless and possibly odor-free are appearing and causing problems for both the police and crime labs. Chances are these will have GHB or one of the GHB substitutes. GHB and GHB substitutes cause problems because of the rave drug culture. This article examines osmolality, the science that looks at osmotic pressure and is based on the number of dissolved particles in a solution. Osmolality could be used to screen beverages that may potentially contain liquid drugs or identify evidence of tampering. An instrument used for testing osmolality is an osmometer. An osmometer can help sort liquid drugs and help identify drugs in liquid. The science behind the instrument is based on the fact that particles dissolved in a solution change the physical properties of the solution and the changes include a lowered freezing point and a higher osmotic pressure. The osmometer has limitations, including: (1) it doesn’t tell what you have, just that somebody has tampered with a liquid by adding something that has a small molecular weight; (2) they are not helpful in screening liquids containing compounds with larger molecular weights; and (3) if the instrument shows no or little difference in osmolality, it doesn’t mean a liquid has not had something added to it. In conclusion, crime labs need efficient new tools to process the increases in liquid sample submissions. Osmolality can be an excellent, low cost, rapid and non-destructive screening tool for the forensic drug testing laboratory.