How do you get rid of a heavy cockroach infestation?

Getting rid of a heavy cockroach infestation with hundreds of German cockroaches or American cockroaches requires aggressive, multi-step integrated pest management because heavy infestations mean many hidden colonies, egg cases, and nymphs in wall voids and under appliances that cannot be eliminated by sprays alone, and typically requires professional help for complete eradication. First, conduct thorough inspection to locate hiding spots including under sinks, behind refrigerators, stoves, dishwashers, inside cabinets, in wall voids near pipes, and in clutter, looking for droppings that look like black pepper, egg cases, and musty odor, and consider using flashlight at night when roaches forage. Second, implement intense sanitation to remove food, water, and shelter, store all food in sealed glass or metal containers, clean crumbs, grease, and spills daily from all surfaces and under appliances, take out trash, fix all leaks, dry sinks, and remove cardboard and clutter where roaches hide and breed. Third, seal cracks and crevices with caulk around windows, doors, pipes, and baseboards to trap roaches and prevent spread. Fourth, apply heavy baiting using commercial-grade gel baits containing fipronil, hydramethylnon, or indoxacarb such as Advion, Maxforce, and Vendetta, placing many small dots every 12 inches near hiding spots, plus insect growth regulators like Gentrol that prevent reproduction, allowing roaches to eat bait and carry it back to kill entire colony within weeks, with re-baiting every 2 weeks. For heavy infestations, hire professional pest control costing $300 to $800 with multiple follow-up visits, commercial products, and warranties, as DIY alone rarely succeeds for heavy infestations.