ABSTRACT:A survey of 61 headwater streams and their watersheds on Pennsylvania's Laurel Hill, an area of high hydrogen ion and sulfate deposition, was conducted in May and June 1983. Trout were absent from 12 or 20 percent of the streams. No fish were present in 10 streams. Thirty‐three streams appeared to contain viable trout populations, 10 streams had other interferring cultural impacts and 6 streams had nonviable trout populations. Significant differences in water quality were noted among streams with and without fish. The streams having no fish as a group had significantly lower pH and alkalinity and higher dissolved aluminum than those with fish. Attempts were made to correlate soil type and geology with the presence or absence of trout. Watersheds with a major percentage of very stony land soil classifications always contained no trout or were culturally impacted. On the other hand, watersheds with a major percentage of Upshur (limestone derived) soils always supported trout. Watersheds with more than 30 percent Pocono Group bedrock supported trout in every case but two, while in every case but one, watersheds with more than 30 percent Pottsville Group bedrock did not support trout. Acid runoff episode data indicate severe transient acidification attributable to atmospheric deposition. It appears that a combination of very stony land, 30 percent Pottsville Group bedrock and high deposition of hydrogen ions and sulfate may result in transient acidification and absence of fish populations from headwater streams on Pennsylvania's Laurel Hil