Appeal by claimant from a decision of the Workmen’s Compensation Board reversing a referee’s decision and award in a death ease and disallowing the claim. It is undisputed that decedent’s death, occurring while he was at work as a milk route salesman, was caused by coronary thrombosis and advanced occlusive coronary arteriosclerosis and followed long hours of labor and some mental and physical stress occasioned by circumstances attending the termination of a strike. One physician testified that the thrombosis was *626“due to extra work and extra mental strain ”, another testified that there was no causal relationship and two physicians who were called expressed no opinion. It seems to be appellant’s theory that because the evidence as to decedent’s activities, and the mental and physical strain to which he was subjected, is not in dispute, no expert medical opinion was necessary to justify an inference of causal relationship and that the board’s decision must be reversed on the law. It may well be that the board might properly have arrived at a result contrary to that reached in this case and that contrary determinations have been rendered and affirmed in eases of undue strain analogous to this. Nevertheless, the question of causation remained one of fact. The medical evidence was in conflict but that accepted by the board was substantial and amply sufficient to sustain its determination. Decision unanimously affirmed, without costs. Present — Bergan, J. P., Coon, Halpern, Zeller and Gibson, JJ.