A comparative study was made of the fungitoxic and phytotoxic properties of an homologous series of sodiumN-alkyldithiocarbamates with 1 to 10 carbon atoms in the alkyl group. The ethyl, propyl, and butyl homologues were comparable to the methyl form (SMDC) in toxicity toMonilinia fructicola, while the amyl and hexyl were less active. A further increase in the carbon chain up to the decyl increased fungitoxicity correspondingly. Germination of barley seeds was inhibited progressively less from the methyl to the heptyl, slightly more by the octyl, and least by the decyl. None of the compounds had any apparent effect on tomato foliage at 10 mM, but when applied to cut stems of tomato or roots of tomato, barley, or cucumber many of the treatments induced wilting, leaf necrosis, and stem collapse. Quantitative data on both fungitoxic and phytotoxic effects were obtained from the emergence of peas planted in sand–vermiculite infested to various degrees withPythium ultimumand drenched with a series of concentrations of each chemical. SMDC and the ethyl homologue were the most effective in controlling preemergence damping-off, the propyl through octyl progressively less effective, and the nonyl and decyl completely ineffective. Non-emergence due to chemical damage decreased from the methyl to the amyl homologue but increased from the octyl to the decyl.