In 2017 in Poland, cucumber was one of the most important field vegetables cultivated on 13 892 ha and with 2 490 988 tons of production [1]. Cucumber has been grown in Poland since several centuries, however only since 1985 downy mildew as its new disease appears seasonally causing a serious menace to field plantations [2]. First signs of disease infection have usually been detected in the south-eastern regions of Poland at the end of June or in July and then downy mildew spreads to nearly regions in 3-5 weeks depending on weather conditions [3]. Actually, protection against this disease is based on cucumber resistant varieties and sprayings with several fungicides [4]. One of them is Infinito 687,5 SC being a mixture of fluopicolide and propamocarb hydrochloride [5]. The aim of this study was evaluation of Infinito 687,5 SC fungicide usefulness in control of downy mildew in cucumber field cultivation in central-eastern region of Poland.