Greenhouse experiments confirmed that both Botrytis cinerea and B. fabae could infect lentil and cause Botrytis grey mould symptoms. Experiments were conducted under controlled environments to determine the effects of temperature, leaf wetness duration, plant age and inoculum concentration on infection of lentil by B. cinerea. Optimum conditions for infection and sporulation were defined at 15–25°C, with limited sporulation at 10°C but no sporulation at 5°C or 30°C. Sporulation occurred 6–7 days after inoculation when leaf wetness was constantly maintained using humidity tents. Absence of leaf wetness for up to 4 weeks following inoculation did not reduce the disease severity, but reduced the time to sporulation to 3 days after leaf wetness was returned. Increasing the age at which plants were inoculated, from 6 to 18 weeks, had no significant effect on disease severity. Senescent and mature plant material acted as a focus for infection and sporulation. Increasing inoculum concentration from 5 × 10⁴ conidia/mL to 5 × 10⁶ conidia/mL significantly increased the number of plants infected, independent of genotype resistance. No disease developed at the lowest concentration of 5 × 10² conidia/mL.