The extent to which pH values of aspirates from feeding tubes could be used to differentiate between (a) gastric and intestinal placement, and (b) gastric and respiratory placement were determined in a clinical study. The sample consisted of 181 adult subjects, 94 with small-bore nasogastric tubes and 87 with nasointestinal tubes. Data were collected at the time of initial tube placement and again, when possible, after one or two days of tube feedings. Using color coded pH-paper, a total of 247 readings were made concurrently with x-rays to determine feeding tube position. Findings indicated that pH readings were often effective in differentiating between gastric and intestinal placement (p less than .0001). For example, approximately 81% of the aspirates from nasogastric tubes had pH values ranging from 1 through 4, while almost 88% of the aspirates from nasointestinal tubes had pH values of 6 or greater. Only one aspirate from a tube inadvertently placed in the lung was tested; as expected it had an alkaline pH.