Abstract A description is provided for Peronospora lamii . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Lamium album, L. amplexicaule, L. maculatum, L. moluccellifolium, L. purpureum, Ocimum basilicum, Plectranthus parvus, Salvia officinalis, Salvia sp., Satureia acinos, S. hortensis, Ziziphora capitata . DISEASE: On Lamium the parasite forms distinct pale green to brown spots on the upper surface of the leaves. A dense layer of violet coloured conidiophores develops on the under surface beneath these spots. Fraymouth (1956) found, when collecting the mildew on L. purpureum , that the plants had a systemic infection in April while in July and August they were newly infected. Oogonia were found in the leaves in April and August. Peronospora lamii was reported from Uganda as causing defoliation and death of Ocimum basilicum . GEOGRAPHICAL DISTRIBUTION: Africa (Ethiopia, Kenya, Tanzania, Tunisia, Uganda, Zimbabwe); Asia (China, India, Israel, USSR); Europe (Austria, Britain, Czechoslovakia, Denmark, Estonia, Finland, France, Germany, Hungary, Italy, Latvia, Netherlands, Norway, Poland, Portugal, Romania, Sweden, Switzerland, USSR, Yugoslavia; N. America (Canada, USA); S. America (Venezuela). TRANSMISSION: No details but oospores are plentiful and presumably play their usual role in carrying the pathogen over the winter. The fact that systemically infected plants are found early in the season suggests a primary infection from oospores.